Bob is right about the darkroom vendors. There used to be a couple of darkroom guys where you could get stuff really cheap but I guess there's no interest any more to make the trip profitable. It also depends if the seller has made his gas money yet. They'll give away some stuff just to recoup the travel and the price of their table.
Prices are really low on oddball stuff. mainstream cameras can be pricey. You can always offer 'em a lowball amount and see how it goes. I'll probably go.