Buying a used phono cartridge for me would be like buying a used Tooth Brush!
Except that versus a good toothbrush: a good cartridge is 100s of times more expensive, 100s of times more durable (if properly used), can often be completely rebuilt to factory specs for 50-60% the cost of new (depending on manufacturer), and you don’t stick it in yer mouth (depending on your listening habits) -- so bacteria/hygiene isn’t a health issue there.
Buying used is a high risk/ high reward scenario, but buying from a trustworthy hobbyist minimizes the risk. Unlike buying a used toothbrush, it’s not altogether senseless. That said, there needs to be a significant discount in play -- it doesn’t make sense to buy an ubiquitous "50 - 300 hours MAX" used cart for only 35% off list.
