Specifically, I asked about people asking IF the seller had a BIN price when the option was NOT offered in the auction. Someone later mentioned contacting such a seller and making an offer. I don't see these as equivalent. I see no harm in making an offer, which is what I think you are talking about.

As I have already pointed out, perhaps 'sleazy' is not the right word and 'lacking in manners' is more appropriate. Like if you went to get a something valued and the valuer asked you how much you were willing to sell it for it instead of doing what you had gone there for. Kind of insulting and a little stupid on the side. Or if you took a bicycle to have some work done on what you knew to be a fine, old classic bicycle and the LBS told you it was junk and that you should buy a new bike rather than waste your money.

I've never sold anything on ebay, only bought, but if I was a seller I might put a BIN price but if I didn't it would be a conscious decision and might be because I was unsure of its value, or interested to see what it would go for, or not mind it going for less than I thought it was worth or maybe just for the fun of it. If someone then asked me what my BIN price was, or if I had one, or how much I would want to stop the auction, in other words, expecting me to do what I had consciously decided not to do, I would wonder at that person's manners and motives and perhaps their ability to understand English. I might also make a note never to accept bids from that person in the future, although with a memory like mine I would probably soon forget.