How much are the extra costs for a night train?
The extra costs of a night train or hotel train depend on the train you are taking and on the level of comfort you are looking for. In some trains, there are also seats (not only beds), which are available for free. The costs of the bed, depend on whether you travel in a 6-person, 4-person or 2-person cabin. They start at about USD 37 / AUD 44 / EUR 25 per bed. Some night trains, in Spain, Italy and France, have beds only.
Travelling by nighttrain will save you the costs of a hostel or hotel.You can find more info in an online timetable, such as: http://www.oebb.at/vip8/oebb/en/index.jsp. In the details of a specific connection, you will see whether this train has seats, beds, and whether it requires a reservation.
Reservations can be made from 3 months in advance, the earlier you book, the larger the chance of getting the accomodation of your preference.