Those are such "it depends on . . . . " questions.
From reading some of these posts, many of you don't "need" another sewing machine for sewing????
So then it goes to "entertainment/collecting"?
I think being polite goes a long way in any negotiation. I acquired two Necchis for way less than they were worth - even AFTER repeatedly telling the sellers they could probably get a lot more for the machines from a different buyer.
It probably doesn't do much for getting a reduced price if one shows up in a Rolls Royce and flashes a wad of large denomination bills, either.