Rare Nintendo games don't have to be popular to be valuable. Some, like promotional games and Not For Resale cartridges, fetch high prices averaging $3,000-$10,000. Earthbound for the SNES, Barbie ...

Players used an in-game $5,000 loan to make their own dino-zoo in a bid to pay it off. If they succeed, they can sell it off, get an award, and be a better Dr. Hammond than the one in the films.