Just a single sortie is very expensive in just maintenance + supply. You need a whole crew to prepare a plane. Not to speak of the whole infrastructure required

Just a single sortie is very expensive in just maintenance + supply. You need a whole crew to prepare a plane. Not to speak of the whole infrastructure required to train pilots, having places to fly from, teachers to learn from. It all adds up to a huge number, that when you divide by the number of pilots trained, doesn't get reduced by a lot.