F = floor, C = ceiling. Floor and Ceiling flange, or floor and ceiling plate.
I've never heard it called and F&M unless its was mispronounced (I'm tellin' ya, itsa Effen M flange..., not an Effen f and c flange) ;-)
Just guessing here.
It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.