an original 1956 Aerocar--the first flying car to be deemed street-legal in the U.S.--is listed for sale on eBay. And it's only $3.5 million--if you use "buy it now.", but
It's presumably in good shape, with the auction stating that its engine was inspected a couple of years ago, but if you plan on flying this car anywhere I'd recommend a tune-up first--the engine hasn't been officially inspected since 1976.
Of course, for that money you could buy a top-of-the-line personal jet as well as a rare super car, but that wouldn't be nearly as neat as this thing. I want it.