Zenfoldor's way to get games really cheap, because he loves you:

[The Ghost of RubangB]

I've bought used NES games on eBay and at the swap meets in the Classic Gaming Expo 3 years in a row, and at GameStop, GameCrazy, and the old dead FuncoLand. The only games I've ever purchased that never ever worked and were complete duds were at GameStop. eBay's great.