Here is another theory- they get plenty of exposure they wouldnt have gotten, through people spotting it and discussing it on forums like this. Then they either get loads of interest via email &/or watchers.
If it doesnt go in an exchange of email at a reasonable price, they relist it, no additional fee, at the right price and all those watchers are informed via the An Item You Were Watching... system. Clever?
May even try it myself..

Have to be a Free listing offer though.