Right you are: it has to be a Buy It Now non-negotiable price. I missed that. (The couple of second-chance offers I've accepted have been BINs, yes. Since I hate haggling and really am not a very good negotiator I just shrugged and paid "retail", never occurred to me at the time to see if the seller would take less than the BIN....but I see that he can't anyway, not through eBay at least.

Agree with RobbieTunes, this isn't really a question about ethics. It's more about the psychology of auctions, what drives people to want to buy stuff.