If you have to buy from e-bay because you can't get it anywhere else, at any price, then the seller is sitting on a gold mine. That's how supply-and-demand works unfortunately.
Several posters have already said that these bridges are getting hard to find. Scarce means expensive, regardless of the seller's intentions.
(I will agree however that there are far too many sellers on e-bay who are not serious about selling the more common things -- and their prices prove it. These people would rather use e-bay to display their collection, and hold on to it for years if necessary, before selling any part of it at a fair price. If they were true sellers they would know that the money's to be made by moving goods, not by holding on to them.)
Mike