I think what we are see is part of todays economy. These are the type of knives that often spend their lives in drawers, too pretty to use much if at all. People know the knife is worth something and would like to sell(they could use the money), but have not followed the market and are not aware(or could even believe) the ridiculously high prices some of these go for. A wanted graphic on the presentation side turns a $600 knife into multiple thousands.
The sellers are leaving a lot on the table for not putting in a bit of research time. Of course there could be an occasional seller trying to give members a great deal, but I have found that to be a fairly rare case.
Since I haven't been in the position to snag one of these steals Ican only speculate, but I doubt I could take full advantage of the sellers ignorance-but that is IMO and only pertains to me. No one has such an obligation.