The store and the family that run it are very famous now so it operates more like a TV set/souvenir shop than a working pawn shop these days (although they have pawn brokers on hand if you really want to buy or sell something - it just isn’t generally the people you see on the show). However, it was a working pawn shop for decades before the show and a very successful one at that.
I have been there. It is in a fairly seedy part of Las Vegas about 1 1/2 miles from downtown. The cab driver that took me there freely admitted that he knew the whole family quite well simply because he was a drug addict and criminal for many years and often needed to pawn or sell stuff at 3 am to get his next fix. He said he hated all of them because they were assholes to him but consider your source.
People often say that the show is fake based on observations like you just made. My family owned a pawn shop in rural Louisiana for years. You typically get junk just worth a few dollars in a location like that but really valuable and rare things also walk through the door with surprising regularity. We got everything from very rare firearms to prehistoric artifacts, horrendously expensive gold items, rare coin collections and everything else you can imagine. My father kept a lot of the really rare stuff for himself because the people often didn’t know what it was worth and sold things pennies on the dollar or less (this was pre-web and before cable shows about pawn shops).
The whole show is legit as much as a TV show like that can be. The shop was very gritty and real until it got too famous to be what it once was anymore. They pick and choose what items to show and schedule the bartering plus the experts because that is what you have to do to make a show like that but they are all real too.