At least I'm convinced I didn't underprice it. It's selling for more than I sold it for, but he did a bunch of work on it (probably himself), and I think it was the work that needed to be done when I sold it to him. I had no hope of doing that work myself, and I had the fantasy that I was going to be living in residence this year studying to become a world-famous astrophysicist in ten years. Ha-ha.
I only wonder what happened to the caps on the front wheels.