Adding abilities to magic items

[powerdemon]

Hey all. So I know adding magic abilities to existing items is allowed, and that if you add extra abilities to an existing slotted item, that they cost 1.5x as much. I also know you can improve bonuses on items by paying the difference. So an item like Belt of Giant's Strength +2 can be improved to a +4 by paying the difference instead of 1.5x price.

What about an item like Anaconda’s Coils (http://www.d20pfsrd.com/magic-items/wondrous-items/wondrous-items/a-b/belt -anaconda-s-coils)? If I want to improve the Str bonus from +2 to +4, do I need to pay the difference between the Giant's Strenght +2 and +4, or the difference between the default belt and 1.5x the cost of a +4 Giant's Strength belt?

[Bob Bob Bob]

Linkified. This is important because it puts spaces in urls if you don't use this.

So I can tell you right now, this is going to get messy as #@$%. Anaconda belt is a +2 Str belt and a bunch of other things. From the price (18,500) the belt must be the cheaper option (4,000, increased to 6,000 as it's a extra feature). But if you upgrade to a +4 belt (16,000), then that is the most costly ability and the other ability should be multiplied by 50%. And that's assuming that +2 grapple and constrict are one ability, and not two. So maximum price, 34,750 (16,000 belt +4, 12,500 * 1.5 other abilities).

But that's only the maximum. It's entirely possible it should be cheaper because +2 grapple and constrict are actually two separate abilities, one of which has already been multiplied by 50%. They're not on the standard table though, so I can't help you there.