I deal a bit with arty types, and they tend to pride themselves on being able to identify products, along with designers and quoting how many hundred $'s something "costs"

I think it's a bit like nerds and bragging rights in being able to produce good explanations for difficult technical questions. Along that line of thinking, perhaps a stackoverflow karma / community recognition style system might be enough.

yeah at the moment we are doing a point based system where user gets discounts from retailers. unsure what will work best but its something that we going to play around with until we find what works best