I ended up with a big box of non-sport stuff from my days working at the card shop. If memory serves, a customer simply left the box behind and nobody much cared if I took it home with me. So I did and have not regretted doing so ever since. I was looking for stuff to grade when grading was cheap, I got a discount on it, and the market was hotter.
One of the many things I sent in on a whim was a handful of Marvel Stickers from the 1970s.