[jerf]

"Buy for $x, have and not sell for $x, same mathematically."

Sort of. People are being less irrational than it sounds if you account for transaction costs. There's a lot of stuff I might "sell" if I could point a video-game-like pointer at it and right click and hit "sell", and it just instantly disappeared and money was credited to my bank account. Perhaps even more if buying was just as easy and I didn't need to hang on to something like my drill which I don't use very often and I could trivially "rent" it from the market by buying, using it, and selling in mere minutes.

But in practice one-off selling for anything less than $100 or so is a waste of time because there are significant transaction costs for one-off events like that.