Just read this, brilliant stuff, we'd been talking about going over there this year, should have done it 

What a nice way to spend a few days, I'm also interested in the costs etc
You can book a cabin through Wild North tour operator (owned by the Finnish Goverment). Prices per day for cabin enough for 10 people start from c. 60 euro. Winters are cheaper as usually they give 20% discount during winter months (October - March).