The first three lanes of taxis are of companies that offer a fixed price to center: 35€ FixuTaxi and TaksiHelsinki and 39€ Menevä. However, you have to agree with the driver to use this fixed price. If you don't tell him to use this fixed price, they will use a time + per km charge. So it's possible that your friend took indeed a taxi from one of these companies, yet if you don't demand at the start of the ride that you are using the fixed price, they will charge a much higher fare. It's very unfortunate, but you have to be quite aggressive and make sure that they enter the fixed rate on their device and most visitors don't know about this (a fair share of locals neither). Usually drivers pack your luggage quickly and start the ride immediately, not giving you time to even discuss this: make sure you don't close the door before agreeing on the fixed rate. Moreover, once the driver tried pull out a "my card reader is not working today" once the ride was started - this is of course not acceptable. It's a pity that HEL airport taxis have become a stressful situation for many, but it's good to remember that you can move on to the next taxi in the line if the driver seems shady.