The older I grow as a magician, the less I'm interested in owning stuff. I have been giving away a number of my books and magical items keeping only those things that I actually put into use. I now own less than I have five years ago, and sometimes I feel I still have too much.
I give. I don't sell. I don't think I would gain much profit or satisfaction from selling my old stuff anyway. I think giving (or doing an act of kindness for that matter) without expectation of return is an exercise that every human being should do. Own, own, own. Grab, grab, grab. This materialistic, consumerist, cosmopolitan way of life gets very tiring easily.
Trees get to be pruned, snakes shed their skin, people must undergo some kind of death in order to evolve and to grow. Yes, there is a pang of regret when I give away the books that have helped me in my journey. But it is a nice kind of pain. Like getting into a hot bath.
These days I perform ceremonial magic from pieces of cardboard in a shoe box and make talismans from scrap paper. I may have gotten cheaper, but I feel more magic than before.