Given that attempting to film the actual day-to-day life at a pawn shop would result in some pretty boring television, it should come as no surprise that the items you see brought into the Gold & Silver Pawn Shop on the show have been vetted beforehand. Granted, this doesn't mean that the items are plants from producers. In fact, longtime shop manager Travis Benton told the Las Vegas Review-Journal that his brokers "spot unique items and show them to producers who decide if they are worthy of broadcasting."
Another shop employee, Rocco Landi, said, "Once an item is deemed 'possible TV material,' its seller is coached on how to act while on camera. Some people have a great item to sell, but they appear nervous on film. It can take several tries to get it right, depending on the person. ... Producers have cut items from the show because the seller could not 'pull it together' on camera, but it doesn't happen often."
Executive producer Brent Montgomery even admitted that the staging goes a little bit further than that. In an interview with Odyssey, Montgomery said that they have "really smart scripters to feed the characters organic information," and that he's coached the guys on buying stuff they wouldn't otherwise go for if they weren't doing the show. He also said the production team pre-negotiates pricing with the potential sellers off-camera "to make sure that these people will actually sell the stuff at a reasonable price, otherwise they're just trying to be on TV." That's understandable to a certain extent, but it definitely sheds a new light on Harrison's infamous — and regularly parodied — negotiation tactics.
