I once had a buddy who owned a used car lot. He'd bring home a bunch of cars from the auction and sometimes I'd ask, "Who in the hell is going to buy that? He always said, "There's an a** for every seat." Somebody, somewhere, is just drooling over some gun that I might think is not worth the money, and would snap it up in a heartbeat if he could.
I used to work in the antique car restoration business and I think a lot of folks see their guns in the same light. They would see the prices that a 100 point car would bring after having thousands of dollars spent on it and think that their same model rust bucket should be worth only a fraction less, unless, of course, they put new tires on it. But the trouble with guns is, the big bucks go to the originals and any "fixing" or repair is generally penalized instead of rewarded, no matter how well it's done.
Having said all that, I use GB a lot simply because of the convenience. I recently bought a Browning BDA .380 and my FFL said, "Gee, I haven't seen one of those in years." They are not particularly rare but I'd have never got one waiting for one to show up in his store.