Pricing this item is giving me headaches.

[Joker]

How would you price an item which enhances your Warlock invocation Repelling Blast to also include Large creatures?

A quick breakdown of the invocation in question:

Its a Greater invocation, equivalent level 6th. Medium or smaller size target struck by blast must make a reflex save or be hurled 5-30 feet and be knocked prone.

 

[Sejs]

How would you price an item which enhances your Warlock invocation Repelling Blast to also include Large creatures?

A quick breakdown of the invocation in question:

Its a Greater invocation, equivalent level 6th. Medium or smaller size target struck by blast must make a reflex save or be hurled 5-30 feet and be knocked prone.

I'd ballpark it at around 10k if slotted.
It's not granting anything new, and it's only useful if you have a particular feature. Seems about on par with granting a feat that has the same effect. Hence 10k

 

[Joker]

I suppose the price would exponentially increase if it would include larger than large creatures?

 

[starwed]

Seems about on par with granting a feat that has the same effect. Hence 10k

Yet if this were a feat, I don't think anyone would take it.

I suppose the price would exponentially increase if it would include larger than large creatures?

I don't think so. It just doesn't seem to be that powerful an effect: compare to the nauseating blast the Warlock could have taken instead. Being knocked prone is nothing compared to being out of combat for a full minute. And being knocked back matters much less the larger you are (reach). 10-20k seems kind of reasonable to effect up to Huge creatures, to my point of view.

 

[Cheiromancer]

My gut tells me to make it a ring (or gauntlets) for 8,000 gp. So I agree with Sejs. Seems like there should be a drawback besides cost; have it use a slot, or be of limited use, or something. A rod would be fine, too.

I dunno about exponential scaling, but if +1 size is 8K, maybe +2 sizes is 32K, +3 sizes is 72K, etc.? Quadratic scaling (plus squared x 8K).