I'd say a fair price for 10 would be around $15-20, since custom chips range from about a $1.00/chip for small runs to nearly nothing for HUGE runs. Of course, this is all dependent upon what type of chip (Clay vs. ceramic, weight, etc.)
I think using a ten chip stack would probably be the best bet for orders. Anyone wanting more can order multiple stacks. I'd say this is pretty doable.
Another idea, if there was enough interest, you could use extras and place one in each of the preorders of the game as a surprise "Thank You" which could generate interest in them as well. This might not be feasible, but its fun to imagine...