Nothing ........ but where it's going to cost money is when they stop charging £40 to print a boarding pass, or £160 if it's a family of four, or when they stop charging £50 to check in a bag that's a millimetre too big, or whatever it is for a bag that's 500 grams overweight, or when they stop trying to sell scratchcards on the flights. Then the staff start to lose their bonuses for 'extra ancillary income' and they are going to be miserable and those smiles won't be there.
Think they make SFA from it because whole issue of charging was to change culture of people just turning up and queueing.............pretty much worked as well.