reservation fee

Information like this is available on the German Rail (Bahn) website. Standard price for one bed in a cochette-6 is €128,60. If available, the standard price will always be the same. There are also discounted, non-refundable, advance purchase Savings Night tickets. The price for these depends on whether the lowest prices are sold out. Right now, for Feb 15, there are Savings Fare ticket available at €49 for a couchette-6. If you are talking about the surcharge for that accommodation with a rail pass (sometimes referred to as a "reservation"), it's €20. When you click on "check availability" on the Bahn website, you'll get a table of fares without a railpass. At the bottom, select "Book only extra charge". On the next page, select "pass offer" and continue. The next page will allow you to book the pass holder "reservation".