I have no idea really, but I could take a stab at it. Base cost: The coin is worth at least this much simply due to it's metallic composition. + Historical significance: A gold coin from the lost kingdom of Jackoffia is worth a lot more than a pretty gold coin from the guy on the infomercial. + Rarity: So I've got a few of these gold coins from the lost kingdom of Jackoffia. But one in particular is a double-strike, the only one known to exist. I can't put a $ value on any of that because I haven't got a clue. I'm sure it could be worked out through researching current market values.