1. He probably won't be paying full charges at the airport. Most carriers usually have different rates, I'm guessing EI having the best deal with operating long haul services. The only carriers that pay full prices are the ones that only offer a limited number of services such as MON and FCA who operate charter flights.
2. Most FR flights don't make a profit off of air fares, but include onboard service (drinks & duty free etc.), car hire, hotels, credit cards - the list goes on - they end up making HUGE profits.
3. IF they did pay full charges then they would certainly make it up at some of the airports they fly to. Remember Derry PAYING them to fly there?!