IMO, the used bike market has been over inflated for years. However most of them don't seem to be selling at the prices ask. If you watch you'll see the same adds re-listed forever.
You do occasionally see a sane price listed. And even a few steals from those just wanting to rid themselves of inherited stuff or simply tired of it taking up space. But those go quick and at those prices buying unseen is worth it many times.
How do you find them? Spend all your time running the search engines of every site and reading classifieds. When you decide it's too much bother, buy new.