Custom Magic Item Pricing Hypothetical

[bokodasu]

Let's say you were crafting a wondrous item that used Summon Nature's Ally I, but it could only summon monkeys.

Would you make it cost more because it's focused, or less, because it's less useful than an actual cast of SNA? Or the same, because all of the above?

Related: how come bags of tricks cost so much? I guess they have an implied "speak with animals" on them, since it doesn't say you have to be able to communicate with the summoned animal, but it's not listed in the spells you need to craft one.

[PinkysBrain]

It would cost less.

Bag of tricks costs so much because of duration.