~~~ once you've bid on it, is having been winning high-bidder and someone contacting the seller with: "The --- you sold is worh far more than what it closed for... and the buyer is fully aware of this since he is an expert in ----. I will offer you much more...."

It happens.

I do agree that contacting a seller and asking to end an auction once there has been bids is low... but there is nothing wrong with contacting that seller if there are no bids; sometimes the buyer really isn't interested in waiting a whole week and simply contacts the seller with "performance history" as part of the proposal.