I remember getting a metric shit-ton of expired film on e-big many years ago when I was on less than a shoestring budget with photography. There used to be deals to be had, but today they are rare to come across. Mostly it's just either junk, and some people just LOVE to experiment with old film due to a certain unpredictability, as if there is some sort of cool factor in doing so. I have no problems with that at all.
But it is really funny to watch some of the prices on FRESH film. That's the part I don't understand either. But more power to the re-sellers for getting more money than their merchandise is actually worth. That's pretty smart, if you ask me.
Plus, don't overlook the thrill that people get from bidding on an item, and beating somebody else to the punch. That might be worth a few extra dollars to some.