I think it's a liitle more complex. I can think of four answers: 1) what the casino will pay you to buy the chips back (zero). 2) what you could sell them to the person behind you in line (an average of $10, (a little less if he doesn't trust you and a little more if he wants the extra win cards chips for betting) 3) what you could sell them to a collector (a small fortune with enough hype) and 4.) the real answer. If you were going to gamble $15 anyway then, to you, they are an exact substitute for that $15. Remember if you win you have $30, so a 50/50 bet produces a $15 expected value. Of course you paid $10 so the net value to you is $5.