Hello all you Germans, Dutch, Swiss, French and Brits,

I have a question about the train tickets in Europe. I know that you need compulsory seating for IC, ICE, EuroCity, Schnellzug etc... How much is that extra fee? I mean the cost that comes on top of ordinary tickets. Since we have the Interrail card, we don't have to pay for the tickets themselves, but only for the extra fee, and I have no idea how much this is.

If anyone could give me a fee, even an estimate, I would be very very thankful!!! This would be very important in estimating our budget for the summer...