Supplement for luggage. Supplement for airport pick up. Supplement because the trip starts at eleven o'clock at night. Supplement in the price per kilometer from a distance of ten kilometers. Supplement because you have not shaved for two days ... Well, the last one is obvious that I just invented it, but if you just arrived in a foreign city and it is a Taxi that takes you to your destination, how can you be sure to take enough money to pay the driver?