Gamefly let’s you rent games via mail ala Netflix. Now they’ve always let you buy used games from their servce, but they’re currently trying to clear stock - From now until Janurary 9th they have free shipping on all used games. I’ve purchased 3 games through their service and not once have I found a disk of questionable quality.

You don’t need to be a subscriber to buy from Gamefly.

Check out their sale at their store - you can search for games on all 3 major platforms as well as all GameBoy models. Most games are in the 20 dollar range but you also narrow down with a specific price range.