You probably nailed it, Pepe. Although there does also seem to be an element of willful blindness involved: when I suggest in all disinterested good will (they never put the size of the bike in the ad and I'm responding to their response telling me and it's not close to what I need) that they take a look at ebay completed items to see what the real world market will bear, or even offer to send them some links, they growl. And a month later, there's the bike at the same price.

Or maybe it's like the old joke about the beggar selling pencils on the street. A kindly, prosperous gent stops, asks how much and is told $10,000. The gent objects that it's ridiculous and tells the guy he's not likely to sell many pencils at that price, and the poor man replies, "Yeah, but if I can just sell one..."

And, again, why just bicycles? They seem, almost uniquely, to be the $10,000 pencils of Craig's List.