I get burned by Buyers from time to time.
just one off the top of my head was a brand new wood plane that sold for 350
about 2 weeks later guy wanted to send it back. said it didn't work right. had to refund him, got the plane back with tons of scratches, damage, and the box had a large hole in it.
as a seller your hands are pretty much tied.
I also have had people switch their broken item with the one I sent, then file a return, sticking me with a broken item.
I have free shipping on like 95% of the items I list, currently at over 1000 items. cant stand some peoples ridiculous shipping charges and would never dick over people like that.
I still do well on ebay but can be a pain for sure