A couple people have mentioned the old rumor that Ditko uses his old original art as cutting boards. Most likely that is an urban legend, based on Greg Theakston’s misunderstanding of what he saw at Ditko’s home. Here’s an insightful analysis of the claim by Bob Heer, which credibly debunks it: http://fourrealities.blogspot.com/2008/08/curious-incident-of-cut-artwork.html
The notion that Ditko would do that to his original art is not consistent with what I’ve read about him. He may not value money that much, or be motivated by it, but he certainly does not have contempt for his own past work.
I submit this to the “cut-up artwork” speculations: When I worked briefly at Marvel in 1969, I was supposed to be an assistant to Stan — assistant editor, I guess. What I actually did was anything that needed doing. It was a small group, and everybody pitched in and did whatever was necessary. Therefore, I not only proofread, checked scripts, checked artwork and did “editorial” things, but I did lettering corrections, small pencil and ink corrections (once they found out I had marginal art skills) and…PASTE-UPS.