For what it's worth...I started collecting in 1985. Bought and sold a lot of books since. I have not made money on every book. But to your point...with Hulk 181, GS XMen1, HOS92, etc...especially right when CGC started...I did rather well. Pretty much every EC book in my collection was bought from the proceeds of a Hulk 181 that got a 9.6 around 2001.
Those days are gone though. When CGC first started, it really was a killer arbitrage opportunity.
By the way....enjoying a Manhattan made with Noilly vermouth, Luxardo cherries, and Bulleit bourbon tonight (not my regular choice for a Manhattan...but it worked)