you keep selling those, i'll bet that you develop a small following, and prices might start to go up as people compete for coins they want in thier set. Also, you should advertise that you will do Custom coins to order (and set your price, so that it is worth your time).
My recommendation would be to sell the buffalo nickels unaltered. They sell for $9 to $125 depending on which kind you have. You are probably carving their value away. Not to mention defacing currency which is illegal :P
