I suppose it depends on where you live, but I live in Chicago and they're plentiful and usually cheap. Those bands you mention are all very common and standard pressings could probably be found for a few dollars in great shape. Collectors' pressings will cost more, of course.
Many places sell used LPs via mail or the web, but I've found the results to be mixed. You never know what you're going to get unless you find a place you can trust. Peoples' ratings vary greatly.
Many places sell used LPs via mail or the web, but I've found the results to be mixed. You never know what you're going to get unless you find a place you can trust. Peoples' ratings vary greatly.