With E-Bay I'm not sure of the hows and why's.... But for example. You see a bike sell at auction for say 5K, when it was realistically worth 3K. Not long after you see a few more turn up with the starting price equal to the last sale price of 5K or more. People see the $ and go crazy thinking what they can score.
A classic case in point is what has happened with 83/84 KX500's on E-Bay recently. My concern is wether all this is legit, as the case with the KX's is that they keep re-appearing, each time slightly more inflated.