No.
A +1 Bashing Shield costs 4,000gp (plus the price of the masterwork shield).
Just that alone means it is +1 to your AC (plus the normal bonus you'd get for the non-magical shield) and when you use it to perform a shield bash it is treated as a +1 weapon.
That last bit is important.
If you ALSO make this a +1 weapon then you pay an extra 2,000gp for the +1 weapon enhancement.
But they won't stack. +1 from bashing and +1 from the enhancement equals +1. So you wasted your 2,000 gp.
In other words, there is no reason to do this. Either keep the Bashing or keep the +1 weapon modifier, but don't do both.
Bashing Shield, 1000g for +1, an additional 3000g to get the bashing. 4000g total, plus the cost of the shield itself. All shields are weapons. You can then enchant it as a weapon, for the cost of doing so. +1 Weapons are 2000g. You still however only have a +1 weapon because bashing only makes it act as a +1 weapon for things like overcoming DR. Total price, 6000g for a shield that does damage as if it were 2 size categories larger. At this point though you can continue to enhance it as a weapon and a shield. Just make sure you have the Improved Shield Bash feat if you want to keep your AC
You add the properties up of each enhancement type before you add the two sets together.
In your example, a +1/+1 Bashing Shield would require 6,000 gold, as you must spend 4,000 Gold to make it a +1 Bashing Shield, and then 2,000 gold to make it a +1 Weapon (which is basically a Weapons Property tax, as the Bashing property already makes your attacks and damage a +1 Weapon).
To expand further, a +5 Bashing/+5 Defending Shield would require you to add the cost of a +6 Armor item with the cost of a +6 Weapon item. This means such a weapon requires 36,000 + 72,000 = 108,000 Gold to enchant.
With the Shield Master feat, this makes you able to Shield Bash with a +5 Weapon, and receive a +10 Bonus to your AC (because Defending property)
Lastly, in case it ever comes up, a Shield calculates its +10 Limit for both Armor and Weapons separately; that is, it can be both a +10 Armor item, and a +10 Weapon, at the same time. Shields are really powerful, but can be very expensive, which means their real strength doesn't come until the late game.
You should only have to make it Masterwork as an Armor. You're never given the option to make it Masterwork as a Weapon, which means as long as the item in question is in Masterwork condition (or has the property) in some shape or form, then it can be made Magical, Weapon, Armor or otherwise.
From the PRD:
Even though some types of armor and shields can be used as weapons, you can't create a masterwork version of such an item that confers an enhancement bonus on attack rolls. Instead, masterwork armor and shields have lessened armor check penalties.
Additionally, here's the Magic Shields entry from the PRD:
Shield enhancement bonuses stack with armor enhancement bonuses. Shield enhancement bonuses do not act as attack or damage bonuses when the shield is used in a shield bash. The bashing special ability, however, does grant a +1 bonus on attack and damage rolls (see the special ability description).
A shield could be built that also acted as a magic weapon, but the cost of the enhancement bonus on attack rolls would need to be added into the cost of the shield and its enhancement bonus to AC.
As with armor, special abilities built into the shield add to the market value in the form of additions to the bonus of the shield, although they do not improve AC. A shield cannot have an effective bonus (enhancement plus special ability bonus equivalents) higher than +10. A shield with a special ability must also have at least a +1 enhancement bonus.
This means that the grand total of a +1/+1 Heavy Steel Shield would be 3,170 gold, as you can't pay the 300g required to make it a Masterwork Weapon, you pay 1,000 gold for the +1 AC, and 2,000 gold for the +1 Attack/Damage.
A masterwork shield has a fixed cost. This is because it does not gain a +1 bonus to hit if used as a masterwork weapon.
So, no, you pay the default masterwork cost once and once only, there is no extra cost for the weapon side of things.
Also note the Guardian enhancement on the weapon side...giving you the option of adding the weapon bonus to your saves instead of your AC, if you also have defender!
A classic Uber shield, when it stacked with Shield spikes, was a +5 Bashing Heavy SPiked shield, +5 Defender Guardian. 2-12 20/x2 dmg, +12 to AC with Improved SHield bash, and a +5 weapon with Shield Mastery. For the low, low price of 134k.
==Aelryinth
I'll start off by saying that text is not in the Core, which is where I took my text from. I won't say it's wrong (as it's from UE), but it's certainly not an original entry in the primary Masterwork sections in the Core. That being said, there are two sets of text we refer to, and that's the subject matter in their respective entries, and determining their sentence structure will determine whether it's plausible or not. I suppose I'll stick with the UE entries, since that's what we're going based on.
For Armor Spikes, we have this:
An enhancement bonus to a suit of armor does not improve the spikes' effectiveness, but the spikes can be made into magic weapons in their own right.
From this, it makes sense for Armor Spikes to be made into Masterwork Weapons. They are considered their own weapon, and are treated separate from the Armor for the purposes of enhancements (though they are otherwise still attached to the Armor itself). They otherwise lack Armor components (and Shield components), meaning it's not restricted to reducing ACP (which it doesn't have).
For Shield Spikes, we have this:
Deadly spikes and bladed projections extend from some shields, transforming such pieces of armor into weapons in their own right.
...An enhancement bonus on a spiked shield does not improve the effectiveness of a shield bash made with it, but a spiked shield can be made into a magic weapon in its own right.
(I'll go ahead and point out that there is a minor typo, "weapon" not being made plural, and I fixed it for simplicity purposes.)
From this, it doesn't make sense for Shield Spikes to be made into Masterwork Weapons. At no point are they referred to being an individual subject to enhance or create, nor are they stand-alone items that function on their own as actual weapons (but Improvised? Certainly). Every reference to Shield Spikes in their entry refers to them enhancing what a Shield could otherwise do (I notice this is probably a reprint update, as this isn't the same entry as we've mentioned before), so there is barely any evidence supporting Shield Spikes being self-evident besides what appears to be yet another misprint in the Masterwork sections of that book.
Most telling (and consistent), they aren't treated separate from the Shield for the purposes of enhancements (and likewise are probably welded on or otherwise permanently attached to the Shield). Lastly, I don't know how you could make Shield Spikes Masterwork, as they aren't considered their own weapons, and based on the table (as well as the entry), are flat gold addon costs onto the item they're designed to fit; Shields, which cannot be treated as a Masterwork Weapon, as per the previous clause.
I've said about all I can say on this matter. The original question is answered and finished. If this devolves into another argument about stacking or whatnot, I'd suggest you make a different thread, so that we may otherwise continue it there (though to be honest, I'd rather not as it would probably end up being another bout of rehashing things).
bY THE rules, the only thing shield spikes do is change the shield's damage from blud to piercing, and increase damage of the shield by a virtual size.
That's it. Full stop. Adamantine, silver, and cold iron spikes do nothing for the shield. Likewise, masterwork shield spikes don't make a masterwork spiked shield, so it's superfluous. Also, you can't enhance the spikes. You can only enhance the spiked shield.
So, yeah, you could create masterwork shield spikes. They'd do absolutely nothing and you'd be out 100 gp, because they don't enhance the shield, just like you don't enhance the spikes magically, you enhance the shield.
Error and a contradiction, but all the weight is on the side of the spiked shield.
==Aelryinth
From this, it doesn't make sense for Shield Spikes to be made into Masterwork Weapons. At no point are they referred to being an individual subject to enhance or create, nor are they stand-alone items that function on their own as actual weapons (but Improvised? Certainly).So it's your opinion that the text allowing one to create MW shield spikes is an error? Does it follow from your reasoning that one cannot enchant the shield spikes as their own weapon that one can only enchant the entire spiked shield as a weapon?
Also, what are the implications for special materials? I've seen people talk about making the shield out of one material and the shield spikes out of another. Do you believe this is legal? If so, what properties does a mithral shield with adamantine spikes have as a weapon? Both metal properties or just one?
If this devolves into another argument about stacking or whatnot...While I can understand your propensity to make this comment, and it's not without some justification, you're tilting at windmills.
I wouldn't call it an opinion, considering the rules back up my claim. But yes, it would be in error, as you can't feasibly make Shield Spikes Masterwork (as a Weapon anyway). And also yes, the Spiked Shield, as a whole, can be enchanted, because the rules refer to the Spiked Shield as a whole, not the Shield Spikes from the Shield, and vice-versa.
As for special materials, it's safe to say, though, that Shield Spikes aren't considered their own weapons (they must be attached to a Shield), which means you'd have to price Shield Spikes as if they were some "other" item (which you can't do with every special material). Even then, since they would be priced as an "other" item, its effects in relation to what they're attached to have no effect on what it is they're attached to.
I'm sure James Jacobs references Shield Spikes being their own thing numerous times. Although James Jacobs is the Creative Director, the rules don't back up his claims, and he's certainly been incorrect and overruled on certain things in the past (i.e. Wild Armor).
As for special materials, it's safe to say, though, that Shield Spikes aren't considered their own weapons (they must be attached to a Shield), which means you'd have to price Shield Spikes as if they were some "other" item (which you can't do with every special material). Even then, since they would be priced as an "other" item, its effects in relation to what they're attached to have no effect on what it is they're attached to.I do not comprehend what you're trying to say here.
Shield spikes have a weight. So doesn't this support the idea that I can buy mithral shield spikes and stick them on my wooden shield?
I'm saying that Shield Spikes aren't weapons in and of themselves, and therefore cannot be crafted as if they were Weapons with Special Materials (and if they ever were crafted through some other means, would not receive the benefits of being a weapon).
They might be crafted as if they were an "other" item (i.e. tables with "Other" in them), but again, don't receive the benefits of being a Weapon, because they aren't a weapon.
So can I craft the shield out of mithral and the spikes are irrelevant and I treat the spiked shield as a mithral spiked shield?
So are you saying that there is no benefit to making the spikes out of any special material?
By the rules, that's correct. I understand that in a real life situation it wouldn't work that way, but the rules are abstract of realism in this regard. I'm saying that mechanically speaking, that's how it's written to function: Spiked Shields and Shield Spikes are separate subjects when crafted from special materials, even when they are both attached, regardless of if you craft the Shield with Spikes or not.
Before it's brought up, this doesn't mean that the Shield Spikes automatically become Mithril when the Spiked Shield is crafted, and that when attached, they're Mithril (and therefore you're paying them to be Mithril for free, and then proceed to detach them for free Mithril Shield Spikes); it means that the Shield Spikes, regardless of what material they're made from, don't meaningfully affect how the Spiked Shield functions as a weapon outside of what the Shield Spikes description allows, and the benefits of the Special Material on the Spiked Shield doesn't necessarily apply to the Shield Spikes themselves, and vice-versa (Shield Spikes made of a Special Material doesn't confer the benefits of such a material to the Shield it's attached to).
The Spikes themselves don't really receive any benefit of being made into a Special Material because they are neither a Weapon or an Armor Item. They're an Attachment to a Weapon, which would fall into an "Other" category like you'd see on tables, which means it receives all of the benefits of being an "Other" item (for example, Adamantine Shield Spikes would have Hardness 20 like any other Adamantine item, but wouldn't confer DR or hardness bypassing and Living Steel Shield Spikes regenerate their hit points over time if they become damaged like any other Living Steel item, but wouldn't allow a Save DC to break/destroy a weapon attacking the wielder).
So I'm confused again.
What are the functional differences between a spiked shield made with a wooden shield and adamantine spikes and one made with adamantine shield and wooden spikes?
The key thing to note is that you don't consider what material the Shield Spikes are made out of when determining what a Spiked Shield's overall material is made out of. In your example, the rules would state that a Wooden Shield with Adamantine Shield Spikes means that the Spiked Shield is considered Wooden for all intents and purposes. This means that a Druid could, by the rules, use a Wooden Spiked Shield, but could not use an Adamantine Spiked Shield, as the former is primarily Wooden, and the latter is primarily Metal. Some could rule that Druids would have to get Shield Spikes specifically crafted to their shields in order to properly use them.
For further information and insight, here's a Relevant FAQ. As to what a Spiked Shield is constituted as, ask your GM. My personal opinion, the Spikes would be considered out of the equation, as the Shield portion is more prevalent, meaning whatever material the Shield itself is made out of (and not the Spikes) is the material you treat it as for benefits (i.e. Adamantine Spiked Shield bypasses Hardness less than 20).