I did today, I saw a 50cm specialized allez sport a few days ago going for $150 and wanted to get it for my wife. Today, saw the exact same year/model/color in a nearby town for $450. Offered 300 and stated that I was assuming he got it for $150 a few days ago, and he came back sounding offended that I'd offer $300 and the old trope about assuming things. I mean, what are the odds that two identical bikes go on CL within days? Pretty damn low, I'd think.