I ordered a wedding planning book of sorts way back when I first started planning. It was written by two women who are/were wedding coordinators and it's one of those books to organize ideas as well as it outlines situations and how to handle things.
When it came to the food they said to give the final head count to the caterer a few ppl short (IE if 140 ppl RSVP "yes" tell them 135) to cushion yourself for the people who don't show up. I know that it's to be expected that a few people won't show due to illness or other issues, so at $100/a plate it sounds tempting to do this as to not waste a few hundred dollars, but it seems unethical.
Maybe I don't have enough business woman in me-did you short your head count a few ppl to save yourself any wasted money?
I'm especially tempted since about 15 guests being invited from FI's side are his parents older friends (like 80 yo) and "no-showed" at FI's brothers wedding a few years ago that was 25 minutes away in the afternoon...ours is an hour and later in the evening (late night driving).