A few stories behind each of these cards:
The Aaron RC was purchased off of Becketts Marketplace, back in the Late 2000's. I don't recall the exact price but it was something in the ballpark of $130. I wanted to own the RC of Henry Aaron, I saved my money and was able to purchase it. The Killebrew and Banks RC's were won on Ebay, both for under $100, during the same time period. I couldn't understand how these guys, who were members of the 500 Home Run Club, both so cheap. All of which are in rougher condition, but it matters little to me.
The Koufax, was purchased during COVID. The seller told me that it displays great but measures a touch short of what normal 1955 Topps go for. I have zero plan to grade it, got it for a steal, I'm happy with having it in my collection.
The Minnie, was a throw in from a member on the forum. They were selling 1952 Topps, all lower series. We went back and fourth through a chain of emails, I actually purchased from him twice. Minnie was discussed, but we could never really settle on a price. After I received my second shipment of cards, I noticed the Minnie was in there, and immediately contacted the person, thinking he made a mistake. He told me that because we talked about it so much, he decided just to throw in Minnie for free. This was shortly before his election to the Hall of Fame, so obviously hindsight is 20/20.