I never went to Fantasy Castle. In the 80s I frequented Passport Comics in the valley, and loved listening to Earl hype whatever he had a lot of... One time he had about 20 copies of Superman #123 on the wall, all priced at $10 each. I should have bought a dozen of them. In the early 90s he put Dave Stevens books on the wall with high prices. I had never seen a Stevens cover, and I really liked the art, so I started grabbing high grade copies in the quarter boxes at other comic shops...
As for expensive books just sitting...Cherokee had a copy of Batman #11 in the storefront window priced at $25 in 1966. It was still there in 1968, but had tanned really well by then.