Kilroy said:
This is pretty absurd, if you think about it.
I've made a boat load of magic items over the last couple of years, so believe me when I tell you that it's not absurb at all. I'll try to explain why, but I didn't sleep well last night so I'll do my best.
Kilroy said:
If it's on the weapon, it's only usable with the weapon. If it's on a belt, it's usable all the time. Why would a DM charge more for something that does less?
This is generally true, but not always. Not all abilities of a weapon are only available while they are being wielded, and it doesn't even state that in the DMG. Most of them, however, do only function while wielded, while other abilities just make sense to be available all the time.
For example, you might say that a weapon that grants a bonus to initiative does not have to be carried in hand in order to gain the bonus, it just needs to be carried on your person. It makes sense too. What is a bonus to initiative after all? It's your ability to better react to any given situation with greater speed than normal.
You have to use your best judgement when designed a magic weapon. Make up a list of all of the abilities of the weapon and go down that list one by one, making your decisions as to whether or not that ability requires the weapon to be carried in hand. Just make sure that your decision makes sense.
For example, if I made a weapon that granted a deflection bonus to AC, I would design it function only while being carried in hand, and the description of the weapon would probably have something like this in it, "This weapon seems to guide your hand in combat, helping you deflect the blows of your enemies."
Kilroy said:
If the item is created as a "6 str unslotted wonderous device" then the extra cost is worthwhile, because it frees up a belt slot, but the weapon doesn't need to be wielded to get the str bonus, just carried.
It depends on the enhancement. Some shouldn't function that way, as it wouldn't make any sense. For instance, if a weapon granted spell resistance, it wouldn't kill the game if it worked simply while carried on your person instead of having to be carried in hand. It just depends on the ability.
Kilroy said:
If the item only gives the + while wielded, count it as a the gloves would be.
A weapon is a slot-less item, for the reasons I gave above. Not all of the abilities of a weapon should require it to be carried in hand. It would be a mistake to assume so, as it would also be a mistake to 100% adhere to the magic item pricing guidelines, as the results of those formula's don't always work.
However, there are really only three types of magic items. Slotted, slottless, and those that don't fit into either category, such as wands. Weapons are always slotless, and anything you place upon a weapon is doubled because of that. Slotless items are always more valuable than slotted ones, and weapons shouldn't be the exception to the rule, so I suggest that you always consider the weapon a slotless item, no matter what you're placing on it.
But like I said, the thing that balances out the cost is that some abilities shouldn't require that the weapon be carried in hand, like a spell resistance bonus. Others, however, should require that they be carried in hand, such as a deflection bonus to AC.
For the record, I would also require that the weapon be carried in hand for you to receive the Strength bonus.