Aalborg in Denmark used to be free, but is now ~24 USD for 8 days, $3 per started 24 hours. Parking by the train station is at least $30+ per day.

Billund is $45 for a week and Copenhagen is $70 for a week. That covers the three busiest Danish airports. Parking is cheap, especially compared to the time save by taking the plane.

I get its different from country to country and I guess I'm just really annoyed with the continued insisting that trains are better than planes, when there's almost no benefit to trains in my country. They are practically pointless, out matched by busses, planes and cars, unless you just happen to have a usage pattern that fit exactly with the layout and timetables.

Schiphol Amsterdam is € 124 for to weeks (€ 8,26 per day). Not cheap, but for many people cheaper than taking a taxi.