Mega Man is one of the most popular game franchises in the world and has a mass appeal to the gaming market around the world. Older Mega Man games can fetch a pretty penny and this one is no exception.
A Mega Man 3 NES prototype has surfaced on eBay. The seller goes by mrmark0673 and has a feedback score of 280. Mark does note that the enemies are in different positions as well as some pallet issues/changes.
MrMark is asking for $10,000, but has noted he will take note of any serious offers he receives.