You are mistaken. Instead: "Each +1 of a magic weapon’s enhancement bonus adds +2 to its hardness and +10 to its hit points."
chaoseffect, he is not mistaken, he is just remembering an out of date printing.
Barachiel Shina, that used to be a rule but it was removed a couple printings ago.
I recall that being a rule in like, 3.0
Weables, it was a rule in Pathfinder too, but they removed it.
Here you go:
Core Rule Book Errata Fourth Printing Update
Page 468—In the Weapons Section, delete the Damaging Magic Weapons paragraph. Add the following paragraph in its place:
Hardness and Hit Points: Each +1 of a magic weapon’s enhancement bonus adds +2 to its hardness and +10 to its hit points. See also Table 7–12 on page 175.
Here is the original 4th printing text:
Damaging Magic Weapons: An attacker cannot damage a magic weapon that has an enhancement bonus unless his weapon has at least as high an enhancement bonus as the weapon struck.
Hmmm, I expect this to come up in my game this week. It's going to be tough springing this rule change on my players.
Because it doesn't make sense in the context of all the other rules of the game. Magic items should not be immune to damage just because they are magic. They are not artifacts.
GM: The Titan does 200 damage and sunders your weapon!
Player: What is the Titan's enhancement bonus?
GM: He doesn't have one.
Player: The Titan fails, he cannot sunder any magic weapon.
GM: That...doesn't....make...sense.
(In this context titan and damage are fictional examples of some creature doing ridiculous amount of damage and still failing to sunder a weapon).
Enhancement bonuses still add hardness and hitpoints, that is reasonable. Being immune to damage is not reasonable.
Why was it changed? Now a rusty weapon can destroy a +5 weapon. It makes no sense now.
Only if the wielder of that rusty weapon has sufficient strength.
Assuming a typical steel +5 longsword, you're looking at 20 hardness and 55 hitpoints.
Let's assume you're using a rusty greatsword with power attack at BAB16 and 22 Strength, on average you'll do 31 damage (= 7 from dice + 9 from strength, 15 from Power Attack). So you're looking at three hits just to give that longsword the broken condition.
If it's something a bit more equal, like a one-handed rusty longsword, you're looking at 20.5 damage (= 4.5 from dice, 6 from strength, 10 from Power Attack). So on average you get 0.5 damage past hardness, so you're looking at 55 hits just to apply the broken condition.
The +5 weapon still has a considerable advantage.
I'm going to respond a little out of order, here.
And the Titan example was a bad one. Many a times you can see in fantasy where weapons, or even magic items, could not break so easily. Cause of magic.
And, by the rules, magic does make it so weapons and armor don't break as easily as their mundane counterparts. Previously, it was nearly impossible for a +5 sword to be broken, unless +5 weapons are extremely common in your world.
By the previous rules, even some lesser artifacts (Mantis Blade is the first I found), being nearly indestructible themselves, are incapable of destroying a non-artifact +5 weapon.
Weapons are the most expensive and take the longest to replace, I just don't understand why it's ok to make them easier to destroy. Or even sensible.
It's only "easy" in comparison the previous rule, which made it nearly impossible. It's still quite difficult.
If you're really looking for a non-artifact weapon that's extremely difficult to destroy, you're looking for a +5 adamantine weapon. It's unclear to me whether the 1/3 boost in HP from adamantine should be applied before or after the enhancement bonus HP increase, so let's go with the more permissive ruling. That +5 longsword from earlier with 20 hardness and 55 HP ends up with 30 hardness and 73 HP when made out of adamantine. Suddenly, that sundering greatsword from my earlier example is only getting an average of 1 damage past hardness per hit, and will require 37 hits to give the longsword the broken condition.
That is by no means "easy".
Heck, I don't even understand why a cloak of resistance +5, which can pay for an entire village, is easy to destroy as a commoner's cloak. I am surprised characters aren't spending half the game time replacing easily destroyed items.
I think this is twofold.
1) Many DMs shy away from sundering. Most players don't find it particularly fun to lose their magical gear, so the DM must use it in moderation. If it happens too often, players will either feel like none of their items matter because they'll just get destroyed soon, anyway, or they will feel like none of their items matter because when they inevitably get destroyed, they'll find something just as good to replace it 5 minutes later. In both cases, the fun of those items is diminished.
2) For a lot of items, you can reasonably expect to replace them fairly easily. Most humanoid enemies at high levels are likely to have a fairly good Cloak of Resistance, or else their saves are going to be a bit low compared to the party's DCs. Thus, if the players do lose their cloak, they'll quickly have a new one.
Barachiel Shina, comparing how easy it is to destroy magic items in the game to other fantasy sources is a poor comparison at best and apples to oranges at worst.
First, there are many elements of standard fantasy genres that this game breaks.
In normal fantasy genres magic weapons are RARE. They are often the equivalent of a Pathfinder artifact in rarity. Of course they would be difficult to destroy.
In Pathfinder magic items are commonplace. Break a magic weapon? No problem, youll get a replacement soon enough or can just fix it with a spell!
Second, you have to look at the internal consistency of a game, not consistency against external elements such as other fantasy games or settings.
In Pathfinder it was inconsistent that you could not damage a magic weapon when just about every other magic item could be readily damaged or destroyed. It was effectively an "I am immune" button to one aspect of the game.
Is it a part of the game that is not always fun? Sure.
Does that mean that there should be a rule to make it nearly impossible to break weapons? No.
Especially since, as ZZTRaider stated, there are numerous ways around it. Adamantine, hardness, etc.
Ultimately, if you have a GM that is constantly sundering your weapons then the issue is probably with the GM and not the rule because a GM who really wanted to destroy or remove your weapon can get around the old rule rather easily.
By the time you can afford a +5 weapon, you can easily get a Hardening spell cast on it. You can also get a Fortifying Stone for 1,000 gp.
/cevah