Take the sage advice of this member:
I know the guys are being rough on you and I know you want a good deal however a Supergrafx almost never goes for under 200, I myself paid 300 for one that did not work with 3 of the sgx games. Cost me another hundred to have it fixed and modded.
Your best bet if you want to score some type of deal like what you are looking for is try to snipe something off ebay at the last second.
I am not trying to be a dick to you just trying to bring you back down to reality as far as prices.
Although I would take what he has to say with a grain of salt, since he was foolish enough to post this nonsense:
I apologize for getting nasty but no one gives me attitude unless they wanna throw down or get a gun in their face
Since you're a valued contributing forum member unlike that idiot, and you don't just troll the forum looking for deals, I'm sure that many people here will be happy to sacrifice hundreds to thousands of dollars and cut you a great deal on the game that most people new and old have been looking for for years.
