It can be expensive. Most wont do small runs so you can expect to pay around $500 from idea to completion. Here are a couple links for you:

http://www.nevadajacks.net/custom_poker_chips.htm

http://www.pokerchips.com/advertising/adchips.html

I didnt have oen made for me, but for my home game. Came out great! And I can say I have my own unique chip that no one else has...