Most, if not all, shows like that are based on a real concept that they run with and modify to make it more interesting for tv. There really are people that buy out storage units and part them out for profit but it's not like what you see on tv. Theres one local auctioneer that does it, buys them in the bigger cities around us and brings it all back here and auctions it all piece by piece. I usually try to go to their auctions because you have absolutely no idea what they might come up with. Things like car stereo stuff and aftermarket wheels and odd accessories don't sell well at auction out here, I've scored a few deals. There was a set of genuine dayton wire wheels one time with wide white walls on them, really nice shape but the spindles/knockoffs were missing. They couldn't get a bid at first and they eventually sold for $40 for the set to some farmer, who I guarantee used the 14" tires as rollers for some implement and chucked the daytons in his iron pile.
People really do run around the country "picking" old barns, but that show is fake too. Maybe not completely fake, but they plant a lot of the big $$$ rare stuff you see being pulled.