The papered show horse isn't the problem, generally anyways. The problem is the people who breed because the love their horse even if it has terrible confo, not registered... then they breed to the random stud down the road.
People who breed expensive horses generally put a lot of thought into the foals in order to get the best possible. Which greatly increases the chance that the foal will have a lifelong home... Little Daisy down the street with the straight hocks, ewe neck, long pasterns, long back, and bad attitude from crappy training isn't so lucky. Her value is crap. The well-bred horses tend to keep their value even in a bad market or at least they only lose a little.