paired weapon property value?

[Darth Stabber]

So assume you have a pair of +4 equivelent punching daggers, and you wanted to add a feature that requires the use of both of them, in this case effects of the two weapon rend feat (phb2). What would cost to add that, or a similar effect that would only work when using both weapons, and how do I achieve this aim ruleswise? There is an underequipped twf assassin in the game i'm running, they have the daggers, but they've been neither used nor identified, so I have a little time to sort it out.

[BowStreetRunner]

I would give the ability a flat value instead of counting as an equivalent enhancement bonus (like how an 'aquatic' weapon is just a flat 2000gp extra instead of an extra +1 equivalent). Not sure what the cost would be for an ability that grants the equivalent of a feat, but I would use that.

[Devronq]

So assume you have a pair of +4 equivelent punching daggers, and you wanted to add a feature that requires the use of both of them, in this case effects of the two weapon rend feat (phb2). What would cost to add that, or a similar effect that would only work when using both weapons, and how do I achieve this aim ruleswise? There is an underequipped twf assassin in the game i'm running, they have the daggers, but they've been neither used nor identified, so I have a little time to sort it out.

I cant remember how i came to this number but i feat is worth about 10,000gp ish +10,000 more gp for each feat in the prerequisite of the feat depending on the feat. This seems a fair number for this feat.

[Agent 451]

I cant remember how i came to this number but i feat is worth about 10,000gp ish +10,000 more gp for each feat in the prerequisite of the feat depending on the feat. This seems a fair number for this feat.
Arms and Equipment Guide p. 128 has rules for pricing artifacts that grant feats. They are quite similar to what you suggest.

[Darth Stabber]

I cant remember how i came to this number but i feat is worth about 10,000gp ish +10,000 more gp for each feat in the prerequisite of the feat depending on the feat. This seems a fair number for this feat.

Sounds good to me, I can make having TWF a prereq for getting that benefit and not make it too expensive. Is that cost per weapon or would I spread it across the 2, and would there be a discount for doing so (since you have added the additional difficulty of requiring the specific pair)?

[BowStreetRunner]

Sounds good to me, I can make having TWF a prereq for getting that benefit and not make it too expensive. Is that cost per weapon or would I spread it across the 2, and would there be a discount for doing so (since you have added the additional difficulty of requiring the specific pair)?

I would apply half the cost to each weapon, since it doesn't function without both. I would also consider the additional restriction worth an additional discount. However, the only such discounts I've seen in an example are for a skill requirement (10%) or a class or alignment requirement (30%). So I am not sure about something that requires both of a pair. The Magic Item Compendium has item sets with collection benefits for having two or more of the set, but I don't know that they explained the cost of creating custom sets. Maybe someone could reverse-engineer the cost from some of the examples?

[Vedhin]

I would apply half the cost to each weapon, since it doesn't function without both. I would also consider the additional restriction worth an additional discount. However, the only such discounts I've seen in an example are for a skill requirement (10%) or a class or alignment requirement (30%). So I am not sure about something that requires both of a pair. The Magic Item Compendium has item sets with collection benefits for having two or more of the set, but I don't know that they explained the cost of creating custom sets. Maybe someone could reverse-engineer the cost from some of the examples?

Summarized from the sidebar on page 193 of the MIC:
2 piece benefit = 10% the combined price of the 2 cheapest items
X>2 = 25% the combined price of the X cheapest items
capstone = as much as 30% combined price of all items.

Magic item set benefits never add to base cost, the cost is in the slots used.

Edit: and yes, an item that grants a feat but requires all pre-reqs to be met is 10,000gp by the A&EG.

[BowStreetRunner]

Okay, so going off the info that Vedhin located, then this would mean the set ability for paired weapons would not increase the gp cost of the weapon set (the real cost is in having to use both hands to wield the weapons), but could only be added to a pair of weapons whose total cost was 10 times the value of the added ability.

So to use the example of a set ability worth 10,000gp, this ability could only be added to a pair of weapons whose total ability was 100,000gp.