dgolds:
A person who flies once per month (or once per week) does not cost the airline. Remember, it is all about yield management and the airline needs to fill a minimum amount of seats to make that flight profitable.

I always try to book the best fare as my company expects me to do so. PremEx said it best: Loyalty. I then tell people how good UA treats me which means free word-of-mouth advertising for UA. How much is that worth?