At long last, EarthBound is coming to the Wii U's Virtual Console later this year, but if you can't wait, and you have a ridiculous amount of disposable income, an eBay seller is now auctioning the ultimate in collectible cartridges.
This prototype cart of EarthBound is so rare, it can't be given a grade by the Video Game Authority, other than NG—"no grade." That's because the VGA grades are based on comparative values, and as a one-of-a-kind item, this prototype has nothing to which it can be compared.
The seller supplies images of the cartridge playing the game, indicating that it is functioning, although he then sent it off to the VGA for grading, and it's been sealed in a plastic box since. He doesn't advise prying off the box in order to play the thing, as it may damage the cart. He notes that complete copies of the game graded by the VGA have sold for more than $4,000, while regular versions typically command prices in the hundreds.
Prototype: Earthbound SNES Super Nintendo Game VGA Proto! [eBay, h/t Kaiser499]