The high availability of the financially gullible willing to pay the high price inflates the value of used hardware for the rest of us. Especially with a pool of buyers the size of the internet.
Capitalism works all right.
If anything, it's these buyers that are the issue though. Why fault the seller for asking more when they know they'll get it?
Anyway, it's still a free country, and it's not like we can (or should) police all the gullible. Even if that happens to be an amusing concept.
Maybe if you see someone paying too much you can politely offer them a tip on where to find it for less? You're sure to get a dirty look from the seller, but hey - it's a free country right?