I've heard of people doing this kind of thing just to increase their feedback. The high bidder is a zero feedback guy; it may well be one of the seller's alt-nicks, so no actual transaction takes place but he can give himself feedback. This is obviously not allowed but it can be difficult to track people doing it.
ebay does have its fair share of idiots though, so I wouldn't be surprised if it was genuine. I use ebay for all my lego purchases and every now and then I see two or three guys placing insanely high bids on items because they haven't bothered to see what identical items have sold for in the past.
