I have seen high end knife dealers at some gun shows, and to some, their knives are worth all the money in the world, and your customs are either nice, but priced too high, or just junk that is priced too high. Some have no idea what you have, and others are very excited and only want to pay a pittance. Some are honest, and tell you that they would like to trade rather than part with money, and that you might try selling it elsewhere, but that their offer still stands. I was surprised taht I was able to sell some knives, production knives, the weekend before Christmas. Right now, knives that are cheap are going to be flying off the tables at any show you go to, and the customs are probably going to sit for a long time. There were three types of knife dealers I saw at that show. A couple of tables selling junk and Benchmades and military surplus, a couple of tables selling junk, and a couple custom knife makers. The junk and the military surplus sold well, from what I could see, and the custom and Benchmade knives sat. I was offered deals on several Benchmades I picked up and looked at, but I had to pass, I had already over extended myself on slipjoints.
The rare and vintage collections is an attention grabber and b.s. Any collector at a show will pay good prices for something they are hard up to get, or which commands good prices.
Take a look at all of those Benchmades/Spydercos/Kershaws/Case etc selling at the gun shows. You've got somebody that has to lug all of these knives around to all the gun shows, all year. He might store his knives in his house, but he usually just sells at shows. He has overhead in that he has to pay for his table. Compound that for a dealer that has high end rare knives. He might look at your Brend, say it isn't a Randall or xxx knife, and hand it back. The chances are very small that you might find a dealer that knows what you have. He might try to undercut you, or just plain flat out tell you to try selling it online.
If you luck into finding a dealer with some custom or high end knives on his table, take a look at some of the knives they have and get an idea for what you want to trade. They will most likely offer or counter offer a trade/cash for your knife.
I have been very lucky in my dealings with knife purveyors at gun shows, in that most are ethical and knowledgeable.