Just thought I'd relay the story of the auction I went to that was attended by Ton and Allan from AH. It occurred in Brookline, MA on 3/21/11 (I bought a unit at this auction, so got the date from my records). This auction was touted as "Boston" on the episode in which it was featured. There were 7 units up for sale and the AH guys bought 3. The bidders were real folks and not extras, though we all got paid $25 for appearing in the show.
On the Boston episode, they showed that 2 units were bought, neither of which looked that great in the few seconds we got to look inside. In one, they found a great vintage bike and some valuable, random bike parts. In the other, there were about 8 6 cu ft Home Depot boxes, 15 very large filled trash bags and one antique gun used to shoot a bomb into whales for whale hunting.
After the auction was over, the team asked some of us to stay behind and do some fake bidding so they had extra footage for the show.
By coincidence, my brother (who was with me in Brookline) went to an auction in West Boylston that Ton and Allan showed up at (this was the "Worcester" auction in that episode). Again, they bought 3 units and showed incredible finds from 2 (I think) units, including a tank gun barrel and an antique safe, valuable in its own right (as I recall, in their wrap-up of unit cost vs. profit, they claimed the safe was worth more than $1000).
I chatted up one of the members of the production team at the end of the auction in Brookline to find out what they did with the leftover stuff in the units after the show was done. He said they'd look for local auction buyers to sell the remainders to. I gave him my number and he called up a few days after the Brookline auction. He offered me the leftovers from their 6 units for $600, this included the safe allegedly worth $1k. As it happened, the unit we bought in Brookline was the worst unit we'd ever bought and we were burned out from hauling trash and making dump runs so we passed up the opportunity to clean out 6 units in short order.
I have to say that these great finds in 4 out of 6 units purchased for that episode can lead a thinking person to only 1 conclusion (which most of you have already done) ... the good stuff is added to the unit after the buy but before the filming begins. It does make for much more fun viewing.