What I think is behind some of the high prices, for items when there are only a few on the market: the seller sees that no other copy is available on the Web, so sets the highest price they think they can get away with for some sufficiently desperate purchaser out there. Then over the next year or so, along come another 20 sellers with copies they've found, and they successively undercut each other. The seller with the expensive one won't have the time (and probably not the inclination) to undercut the undercutters, so the result is a gradient from very cheap copies in uselessly damaged condition up to ridiculous prices for a copy which, while doubtless very good, isn't worth what's being asked for it.

The charity I work for sells second-hand books over Amazon (Joe has seen the office where we do it). I once got an email from another seller complaining that we'd undercut them and would we please increase our price to match theirs? I didn't bother to reply - anybody who doesn't realize how illegal that is won't ever get the concept.

That stuff about Amazon's "Buy Box" and their deceptive pricing was news to me. I thought that sort of thing was straightforwardly criminal activity just about everywhere.