Back in the 1970s, I haunted used stores and flea markets looking for long-out-of-print, genre-related items. Once in a while I'd actually find something that I was crazy about, but was dirt cheap because most people didn't care about it. This was long before the Net and "nerd chic" hipped every seller to what somebody somewhere would flip over. Rare old treasures would change hands for under a dollar.
If I had come across any of those LPs back then, whatever their condition, I would have all but died on the spot.