These shows are fun to watch.
When something is "valued" on the show, they're hoping to get that price based on past sales, etc. I would imagine quite a bit of their "picked" items wind up hanging on the wall with a price tag on it for a long time. Of course it helps having your own show! I'm sure they get alot of customers who just want to visit the "American Pickers" store and buy a souvenir.
As far as "Pawn Stars", I get a kick out of it too, but I'm always frustrated at those folks who find out their item is worth up to $15,000 from an expert, who is also a collector/appraisor, then turn around and sell it to the pawn shop for $7000.
I'll bet that, very often, the appraisor returns and buys the product from the pawn store after the seller leaves. Unless you really want the dough bad, why wouldn't you try to advertise it for sale on craigslist first? Or take it to a local antique auction and see if it will bring more money.
My guess is that the sellers get a chunk of money from the producers of the show for appearing or making a sale on the show that makes it worthwhile.
How about "Swamp People"? Anyone watch that show? I get a kick out of it too.
Chris