The trick is to know how to quickly pick through the booths, and find the ones with actual deals. Or just reasonable prices. This comes best on vendors or small sellers that don't want to haul everything home, or don't know exactly what they have.
Examples: My best friend got a Beretta 92 (DAO) with dimmed but working night sights for $245. A light scuff from a holster at the front corner, but the inside looked like it had never been fired.
I got a Carcano for $40 because the guy didn't know what it was. Sporterized, but what else can you get for $40?
Also, paid $10 for a Czech gas mask for a project, which is less than I would have paid for it and shipping from CTD.
The fair prices are there, it's just tough finding them. They don't come from the big dealers that are just as happy to throw everything back into a van and take it back to the shop. Or from the guys that overestimate what they have--like the $400 Nagant revolver I saw, because "They haven't made these since before WW2!"
Sometimes there's nothing but the small accessories or powder, primers, and bullets that are only worth it because they're cheaper than having it shipped when I can't buy in bulk.
The tough part is deciding whether to go Saturday morning to catch the stuff the sellers don't know but the patrons might, or Sunday afternoon to get the stuff they don't want to pack back up!