According to Dumont, a Volvo S 40 average class vehicle rental costs 60 euros/day plus 45 cents/kilometer in Finland. So, if you travel 3500 kilometers in 14 days, the cost for rental and fuel would be about 2414 euros (3381 U.S. dollars), about 96 cents/kilometer, or 845,5 dollars/person, or 60 dollars/day/person. On average, 4 people together would pay 96 cents/kilometer.
Let's compare prices between two short-distance trips by rail (train) or bus!
Why not travel by train? Sometimes the Finnish railway provides a useful and economic solution for travel from Helsinki to Turku, or Hämeenlinna to Helsinki, etc. Plus, VR may offer discounts for these shorter rail trips.
A one-way train ticket (covering 160 kilometers) travel from Helsinki to Tampere on VR for a group of 4 people. Cost = 90 euros. (126 U.S. dollars). On average, 4 people traveling together will have to pay 78 cents/kilometer each.
Cheaper than driving by car, huh?
Let's look at the same trip by bus... A one-way ticket by Express Bus From Helsinki to Tampere for 4 persons cost = 95 euros. (133 U.S.dollars) On average, 4 people together pay 83 cents/kilometer.
For the same group of four people, a one-way train ticket with VR will cost around 325 euros. (455 U.S. dollars)
Note: ask about a 15% discount for a group of 4 persons and above. On average 4 people traveling together each pay 54 cents/kilometer.
I just figured, traveling by train would be the cheapest option between two, or a series of cities/towns along the train track route. Plus, students get 50 percent off, or consider VR's specials, like a Holiday Pass for "a person of high energy" to travel unlimited distances in a 3-day period.
if you want more flexibility, a car rental in Finland with unlimited mileage is a great option. Visit multiple cities within Finland, friends/relatives, experience the national parks in Finland, go camping, stay at a summer cottage, and see Santa Clause. Generally speaking, you get to travel 2 to 4 times the distance with a rental car, compared to a train. For about the same total cost you get to see more of Finland!