Henry Ford is reputed to have invited job candidates to lunch. When the interviewee salted his food prior to tasting it, Ford decided not to extend a job offer.
So what’s the lesson?
First, when you’re negotiating with someone, whether it’s for a job, a services agreement, or anything else, you can never be sure that they won’t make a decision based on some ridiculous, subjective factor.
The best you can do is to generally conform to social convention. But don’t sell your soul, it’s not possible to please everyone all of the time and there are some people that you don’t want to do business with anyway.
Second, and as a corollary to the first, it’s dangerous to allow yourself to be dependent upon someone else’s whims.