Again, how it's made forms the story around the piece. If you saw that painting in a jumble sale, with no story, it is irrelevant how it's made. But if you know it was painted with someone's feet, then that becomes part of your appreciation of it, and hence it can become more valuable to you.
I have a small framed bit of Chinese calligraphy ("Laugh") in my bedroom. It's nice in its own way, but nothing special. It was, however, given to me by my half-sister who I only got to know for a couple of years before she died from cancer. That bit of art has a particular story attached to it now, and that story makes it worth so much more to certain people (being 'me', basically) despite the art itself being mundane. The story associated with a piece has a value of its own, sometimes entirely orthogonal to the piece itself.
I have a small framed bit of Chinese calligraphy ("Laugh") in my bedroom. It's nice in its own way, but nothing special. It was, however, given to me by my half-sister who I only got to know for a couple of years before she died from cancer. That bit of art has a particular story attached to it now, and that story makes it worth so much more to certain people (being 'me', basically) despite the art itself being mundane. The story associated with a piece has a value of its own, sometimes entirely orthogonal to the piece itself.