I don't know how Mark got the chips, but he apparently has at least a box of each. He started off listing them as sets of $1-$5-$25-$100 with a buy-it-now in the range of $25. People started snatching them up, so he started listing them individually with increasingly higher buy-it-nows. Apparently the demand has dropped and so has the starting price.

My take is, he didn't know what they were worth when he started, and they're worth whatever someone will pay.