I also use very often Fr as my company policy is pretty strict to budget and this is the only alternative to long car trips.
Anyway I would like to add to your considerations that
a) price of food and drinks is high, but at the end of the day it's exactely what you would pay at the cafe in the airport. Also the quality is pretty much the same.
b) Fr is not making transoceanic flights, I think longest one is a couple of hours and if you wanna play the game of buying cheap flight you could also try to resist a couple of hours without snacks.