Interesting, I live in Espoo, and usually, I'm hesitant in taking a taxi from Helsinki city center. 20 min ride (17km) costs me on average 45-50 euro. I don't think this is cheap.
It might not be cheap, but it isn't more expensive than in other comparable countries. I've lived in Brussels where it's cheaper to ride a short distance, but as the distance increases the fare is comparable or bigger because the fare/km is higher than in Finland where the pick up fee is higher.
(Finland: pick up 5,90€ + 1,6€/km/1-2 people vs. Brussels 2,40€ + 1,8€/km/1person or 2,70€/km/2 people).