A long, long time ago I had a flight switched from one airport to another in the same city, and the airline had to foot the bill to take us there by taxi. I remember that at the end of the journey the taxi driver filled in the amount from the meter in a little form and just gave it to my parents to sign. Now they were too busy to notice that the cabbie had bumped up the end price a bit, but not much. I'm sure the system has changed since then to some sort of flat-fee that airlines pay...