Cost of adding magic abilities to items

[Wolfspirit]

Hey, what is the formula for adding to the magic qualities of an allready magic item? Say you wanted to add to the magic bonus of a +1 longsword to make it a +2, what would the cost be? How about a +1 to a +3?

I know I've seen it at some point, but it escapes me and I have 40k gp to spend before the next game

 

[Hypersmurf]

A +1 enhancement costs 2000gp. A +2 enhancement costs 8000gp. It costs 8-2=6000gp to bump a +1 up to a +2.

A +3 costs 18000 - you do the math

-Hyp.

 

[kreynolds]

What Hypersmurf said. Or, quite simply, you pay the difference.

 

[Destil]

Improving weapons and armor is something of a special case. When adding new powers to an item in new ways you increase the cost of added powers by 100%

For instance taking gauntlets of ogre power (+2 Str) and adding +2 Dex (as if you were adding a pair of gloves of dextarity) would increase the value by an added 8k GP.

Also, when making custom items like this, things get a little less clear cut. Formulas like this provide guidelines, but the DM is the final judge in the item's cost.