you really can't price a lens on one abnormally low ebay sale...if you do use ebay to judge you have to, as graham has done, balance it out over a few normal sales.
I once bought a hasselblad v series 50mm CFi FLE lens for about £500 on ebay!...a bargain of course but that does not mean all should be at that price ( if I remember it had no reserve and a spelling mistake in the listing hence few bidders)
Marc