Common problem is people advertising a tread depth that's nowhere near actual.
There's a guy on a local FB Buy&Sell group that I'm on who has been trying to sell a worn out set of junk tires for a few months now, advertising them as "80% tread left!" where anyone who knows anything about tires can see them worn to the wear bars clearly in the picture.
Sadly, someone will buy these thinking they're getting a great deal.
I have had great luck buying used online though. Got a set of 4 true snowtires on steel rims 2 years ago for my Wife's Chrysler 300, inflated and ready to bolt on, about 70% tread left...$225. In July.