Agreed on the bashing thread thing but I am going to share the thing that did it for me.
For many years I sold gear that I acquired that were "surplus to my needs" without problem (one or two, here or there, never a big issue) but what broke me was when I sold a working HP 8663A (passed the Keysight calibration tests) and got whatever they called a "Unit not as shown" and the photos that the buyer used showed a unit that looked like it was tossed off the back of a truck - Funnily the pictures of the box showed it in almost pristine condition - They wanted to return & refund.
Fortunately, I had the delivery insured so FedEx paid out (and strangely returned the unit to me, it's now sitting in storage) - I'm firm in the belief, that the buyer used my unit as a parts mule to fix theirs and then claimed "Unit not as shown" as a way of getting their money back.
YMMV, I just don't think the return on my time is worth it anymore, and certainly not for these units.
TonyG