The only firearm of worth I can recall picking up at a gun show was my 2" 1950 M&P .38 Special revolver a few years ago. Kind of 80 to 85 percent, but shot very little. I paid $420 for it, so it wasn't an
awesome deal, but it was a fair price I think, and I certainly wasn't going to find something like that in one of the local stores.
I also did get a set of non-diamond magnas in good shape (aside from being re-shellacked) for 15 bucks. Put them on my 3" 68-ish model 10.
About 30 years ago, I went to a gun show in a girlfriend's town and got a .303 Enfield with a modded stock for $30, but that gun was too inaccurate to be a shooter. Not the deal it appeared to be.

By and large, gun shows around here are a waste of time due to the extremely high prices.
I hate to say it, but the vendors at local shows don't seem bright enough to figure this out. They appear to be mostly hobbyists who seem perfectly content to sit all weekend at a makeshift booth in an uninspiring convention hall and
SELL ABSOLUTELY NOTHING! You can go hours at one of these events without seeing any sort of transaction taking place. I also hate to say it, but I've seen things that lead me to believe many of them are fishing for under the table sales that will allow them to sell a used 9mm Sigma for $450...IF they don't fill out the federally required paperwork.
Needless to say, I haven't been back to that show in years.