I have no idea whether this is horse manure or not...the seller has no record on e-bay, although he apparently has a lot of other interesting stuff for sale. It seems to me that the seller may actually be Space Adventures, although a quick trip to their web site does not mention any promotion like this.

The point is, there is nothing that would prevent something like this from being real, if it was set up right.

The problem I see is that unless some weird discount was made available to the seller, one would obviously have to bid at least $20 million to pay for the actual trip. And why bother to buy it on e-bay then, when you could just go straight to Space Adventures and set it up for that price? And its not like they have more customers waiting in line with $20 million actually in hand than they have seats.