It's an easy one. Your friend didnt want the bother and cost and risk of listing them on Ebay. You bought them back from him, still giving him a profit for a reasonable price.

At this point, you have the chips, and it's up to you to put the time and energy and risk into selling them. Lets not forget that you got him the chips to begin with. You did as a good moral and ethical person should have done: you informed him of the market value, and you let him know the best venue for him to realize the best potential profit for them. He didnt want the risk, or hassle of going that path. He instead took the money in hand by selling them back to you.

At this point...do with them as you wish. If you want the warm and fuzzy feeling. Take him out for a Sonic burger. I would say giving him cash isn't appropriate here.