Looks like it's the photo op equivalent of a scalped ticket - the person who's reselling it can charge whatever the market will bear, because the tickets are sold out? I'd never buy sports tickets for thousands of dollars, but I know people do.

At least if one gives money directly to the conventions for stuff, presumably some of it goes to the actors as well as all the other people who run the thing. I continue to be irrationally creeped out by the whole idea of cons. :)