I'm paying 300 NOK(€36) for a 5000 MB/unlimited call/sms/mms within the nordic countries. The 1000 MB package is 200 NOK(€24).
Which is again paid for by my job, but many more have this option than a FM receiver without switching equipment or plan.
I have yet to exceed the 5000 MB limit, but the provider I use also have a 8000 MB option for another 100 NOK.
In comparison, if you order a beer in Oslo you will probably pay 90 NOK for half a liter.
Depends on whether you need a separate carrier plan just for that. Most people already have a decent, unlimited data plan on their mobiles, which at least in Finland start from 5€/month. Although, that only buys you 0.5Mbits connection, so upgrading to 10€ plan for 2Mbits might be required. On the other hand, a separate SIM with no calling or SMS functionality will get you 10Mbits for 10€/month.
Plus the hassle of obtaining a new radio to an old car, so that you can plug your 3G phone to it. (At least around here, most car radios do not even have an input where you could plug your phone's earphone output, and even in 10-year-old cars the radio is an integrated model which is not at all easy to replace.)
