Ya pays yer money and ya takes yer chances.
I go to a few of the Saxet shows a year (that one is monthly) and the other two really large ones they have at the old Freeman Colesium.
Sometimes there are a lot of knives, sometimes there aren't. If you are lucky enough to go to one where they have a couple, you will see a ton of used knives as well as some new ones. A few months ago there was a guy that probably had a couple of hundred GECs on hand, and a lot of other high end knives. There is another vendor that makes about every other show, and he has everything from foreign junk to Chris Reeves knives.
As far as buying a good used knife, I have found one good knife priced right in the last few years. Those older fellas that buy those estate and garage sale knives think that an old knife is a piece of true Americana, and they price them as accordingly.
Always, though... lots of guns. For $5 - $7 bucks to get in and free parking, it is a great afternoon.
Robert