Not sports related, but about 20 years ago I was on an antique trip with the wife and we found an shop in Kentucky. It listed as an antique store, but it was more of thrift shop and after about a two minute walk I decided it wasn't worth the time. I told her I was going to wait in the car and by the front door I saw a box of books with some modern history textbooks on top. I stopped and asked the guy at the register how much the books were and he said they just came in and he hadn't priced them yet. I said "okay thanks" and walked out the door. He shouted and stopped me and told me I could take the whole box for $30. I hadn't seen anything except for the history books so I just replied back "I'd do $15." He nodded, I paid, and took the box out to the car.
An hour later we were at a drive in having lunch and I went to the trunk to see if there was anything worth reading on the drive home. At the bottom of the box under about 20 random history books and autobiographies no older than the 60's was a weathered old book. I took it out and saw it was dated to 1840's. At the time I had a friend who worked for a book dealer in Nashville. I made a call and she said she would call me back.
On my drive home I got a call from the BYU library asking for as many pictures as possible. Once home I took all the pictures they asked for and emailed them. 20 minutes later someone else called on behalf of the University and made a low 5 figure offer for the book with half up front and half when it was received. He ended up sending the whole amount up front and I shipped it the next morning. All in it was $15 to $15k in about 8 hours. A couple months later I saw my book dealer friend and asked if she ever earned a broker fee for the sale and she just smiled so no idea what she got.
I'm pretty sure this is the exact book I sold to the University:
https://contentdm.lib.byu.edu/digita...0-1846/id/3718
I later saw another copy sell during covid for six figures.