He might be using one of those programmable boards. They can hold more games though. He could just be reselling the unit. It looks like he sells quite a few machines.
Im a powerseller on ebay and yes, I too have sold a multicade or two on there. However in my experience it seems if you are going to sell a multicade, especially for top dollar, its usually best if you sell a high quality refurbished or new machine. What he is selling could be created by most with little time and a small budget.
Crazy kids...