I would say it's mostly our collective faults. For instance, Sovteks, we all know they're cheap tube amps that can match quality (both tonally and construction) of higher end amps, if not outshine them. So all of us realize that, and look for them on ebay or what have you, and then we tell our repsective musician friends. Then the price goes up.
Same goes with pedals. People hear that the DOD FX90 analog delay is totally awesome and can be found for $35, and then we're all trying to buy 'em up, and their price jumps up to around $60-70.
It's pretty much like that with anything. Collectors are undoubtedly to blame to a degree, but I would think it to be more the working musician who's trying to get by with what s/he can afford and needs. Then these "working class amps/guitars/pedals" end up rising in process.