I search OfferUp, CL and Facebook Marketplace most days, just to see what's out there. With OfferUp and Facebook Marketplace, I've found a greater selection of sellers who don't know what it is they have, which means they're often either wildly overpriced or wildly underpriced. It's all about finding that diamond in the rough.
Every once in a while, I find something that makes it worth my while. I picked up a Surly Pacer on OfferUp a few years back that was far cheaper than it needed to be (cheap enough that I flipped it over on my test ride and ran the serial number through Bike Index to see if it was stolen--it wasn't).
But yeah, a lot of stuff is ridiculously overpriced there. Just gotta wade through the crap.