The used on ebay is the actual upside. The issue is that most people do not need the size of a Pi and using used hardware is reducing eWaste. That said, my personal grab was an Acer refurbished Acer XC-830 J4125 for $89.
While that looks like a nice small-ish tower PC it doesn't seem like it's in the same class as an rPI on a lot of axes, it seems half way between an rPI and a full desktop tower.
