The website of NS (Netherlands Railways) gives the following prices for Amsterdam Centraal - Munchen Hbf
Tickets valid 1 month
The second price is for the 2nd to 5th members of a group (a 50% reduction)
Superretour Apex 7 �103.20 �52.00
Must be booked more than 7 days in advance
Must include a Saturday night
Compulsory reservations
Superretour Apex 3 �155.80 �78.00
Must be booked more than 3 days in advance
Must include one night away
Compulsory reservations
Basistarif �207.60 �103.80
No restrictions
Interestingly, the site makes no reference to single fares (unless I've completely mis-understood it!!)