Some years ago I had my FFL, and sold at gun shows. Gave the FFL up about eight years ago -- it got to be more trouble than it was worth -- but have recently started setting up at shows again, selling knives. Most of what I sell are Bark River products (I'm a dealer), but I also carry some old Marbles, Northwoods, etc. I try to keep my prices in line with what a person could buy these products on-line for. I know other dealers who regularly have good deals on quality items.
I WANT a customer that knows knives, because then they can understand and appreciate why the knife I'm selling is worth $100.00 when they can buy one that looks similar for under $20.00 three tables away. The bottom line is that I will not carry any knife in my inventory that I would would not be pleased to own myself.
Having said that, let me also add that I am very often amazed at the prices that SOME individuals are asking for . . . junk. There seems to be a school of thought that thinks any knife that appears old or beat up must be a valuable collector's piece. I guess someone must buy that stuff, 'cause these guys keeps showing up at shows.