I want to bid on it but not unless the seller can prove to me that it's not stolen property or in violation of an NDA. Because I don't see how it couldn't be. After seeing what Gizmodo was put through over their purchase of a stolen iPhone 4 prototype I want to know all the details on how that dev kit is free and clear.
The seller's Twitter icon is furry porn, which isn't confidence inspiring regardless of whether or not that's a real dev kit.
It's also worth noting the eBay listing puts that dev kit in Delaware, but the seller's twitter location claims to be Raleigh, NC.
Epic is in Cary, NC - that seems the most likely place where it could have escaped from.
Microsoft also has a campus near Charlotte but I don't think they do any XBox development there. I've actually been there twice and was told it's mostly support for government agencies.