He probably got so many dups the same way vinty SW guys wind up with them... Buying collections and whatnot is a fast way to acquire that much good stuff. usually guys piece that stuff back out though, to reinvest into the main collection they're trying to build.
That's my guess anyway. It was a really impressive collection though.
Not to go off-topic here too much, but is it just me or are the two guys on American Pickers (on after Pawn Stars I think) two of the biggest Hot Wheels (seeming) dicks you've ever seen?
You go to a Pawn shop, and you know what you're getting into (and if you don't, you're a fool). When two greasy douche's show up on your porch trying to screw you out of whatever's of value on your property though, that's a different game to me. I guess I just don't care for those guys.