I always thought I would understand the rules for magic item creation - well, until now.
I encountered two problems:
- A magic armor +4 costs 16000 gp.
Why should a mage pay these 16000gp for a robe +4 if he can simply make mage armor permanent with a "continuous spell effect"?
This would cost 1 (spell level) * 1 (caster level) * 2000 gp * 1 (hours/level) = 2000gp
I think it even gets better when you think about shields. For the double costs as above (2000gp * 2 (because of 1/min per level)) you can have a floating magic "shield" spell around you all the time without the negativ effects of carrying a shield. A normal shield + 2 would cost the same and you would have to equip it, carry it around and so on.
Oh, I didn't mention the immunity to magic missiles...
- Assuming that you want to cast alarm permanently on an item or area. Why should you bother to wait till level 9 and cast Permanency? This would cost you 2500 gp. If you use a "continuous spell effect" you only pay 2000 gp (same calculation as with mage armor)
There has to be an error in my calculations! Perhaps I got the whole "continues" thing wrong?
Hope someone can help!
No your calculations look right to me.
Normally I like to put limitations on continuous items like that. Using the uses per day rules as a GM I would say you can use it 5 times a day. If you were to bring the caster level up to 4 I would let it work 24/7 since you have 5*4 = 20 hours.
That cost is 8000 which is still cheep but you can not add armor bonuses to the item like you can bracers of armor.
If you read the 3.5e SRD, it has this little gem listed under "Magic Item Gold Piece Values".
Not all items adhere to these formulas directly. The reasons for this are several. First and foremost, these few formulas aren’t enough to truly gauge the exact differences between items. The price of a magic item may be modified based on its actual worth. The formulas only provide a starting point. The pricing of scrolls assumes that, whenever possible, a wizard or cleric created it. Potions and wands follow the formulas exactly. Staffs follow the formulas closely, and other items require at least some judgment calls.
There's also this part:
The easiest way to come up with a price is to match the new item to an item that is already priced that price as a guide.
Which brings up the whole "+4 armor bonus has a defined cost, so use that instead of an item with a continuous mage armor spell on it".
Also note that a stone of alarm already exists for 2700gp. It's slightly more versatile, which is why I'm guessing the added cost. That or it's "value" is estimated at higher than simply a permanent casting of the spell.
Coming up with gold piece values for item creation has always been a DM adjudication thing. 3e is simply the first time they tried to come up with some level of uniformity for the process, however it's still called "ESTIMATING" for a reason.
One reason for a player not to make your robe +4 (mage armor spell) is due to nasty GMs who may find all kinds of ingenious ways to destroy said object, which would be much easier than doing so to regular armor.
The continuous Mage Armor probably would have to get bumped up in price a little more since it'd effectively be the same as +4 Ghost-touch Robes, since it's a force effect.
That's probably a bit to nit-picky though.
Creating your own magic items and spells is part of the fun of being a spell caster and taking those feats though. After all, a lot of the iconic magic items in the games we play today were thought up and created in the games of the past! :)
The trick to balance it is to put some kind of limit into effect that would help reduce the cost a bit. Maybe you need exotic components you actually have to go get yourself, entailing a long quest for a rare gem or hand picked flower. Perhaps it only functions for so many hours per day and you have to activate and deactivate it.
If it helps add into the fun of the game, no reason to penalize you for something your actually willing to earn.