@Seljuk22
The taxes are relatively high, but not higher than in many other EU countries.
Looking for the reasons of a very minor LCCs penetration, I could point at couple of things. For some carriers (like Ryanair) Finland doesn't seem to be an ideal partner, as the attitude here has mostly been "everybody should be treated equally, no preferencies". That's why Finland loses in comparison to many other countries. The local administrations might be unwilling to "advertise" some carriers as it smells like giving some dubious support or alike. Moreover, there is no low-cost terminal at HEL nor the low cost airport nearby.
There exist, however, some new trends in Finland as well. Vantaa airport has already started granting some preferencial discounts while starting new routes, at least one Finnish airport will change the ownership this summer (Lappeenranta will be owned locally). Things might change.