Bought a sterile Peter Bauchop Witch off of a table at a gun show for $75. Seller had gotten it in a box of stuff at an estate sale. I didn't have the money at the time, and asked if he'd hold it for me until the next day. He agreed, and I was off to secure funds. The next day, I was back with the cash. Before the money traded hands, I asked him if he knew what he was selling? "A knife." So I told him what it was, and what it was worth, and he smiled. Then he told me that about 5 minutes after I had left his table, a woman dealer from a nearby table, who had seen it when we were talking, offered him $300 for it. She was a dealer, but was also a buyer for rich client in Kansas City. He told her we had a deal, but if I didn't come back it was hers. I told him I was surprised he didn't just sell it to her. He said thought about it, he didn't really need the money, and would rather see it go to someone who would actually appreciate it.
That was 20 years ago. It's within reach as I type this.....