I'm kind of worried about the fact carting a dragons hoard out of the cave is a 0-level spell. boom, 1,000,000 lb in gold becomes 1 0lb diamond... I would just have currency be in gems, you can carry as much gold as you want, as apposed to the weight problem for commoners... heck change is easy, just carry around 1 gem as their wallet, and have the creditor extract x gold from it.
great magic trap idea. take 1 massively expensive gem, place it on a modified TG&G spell trap(modify the spell to convert gem to copper pieces)... boom, one tide of crushing metal.
The fluff seems nice, explains why their is still diamond dust for resurrections, and why gold isn't a non-renewable resource like in "sorcerers wheel".