CNL (www.citynightline.ch) has great train service between Munich and Amsterdam. You might get a SparNight fare for less than €99. Regardless, you will be saving the cost of a hotel, the flight, and getting to and from the airports. Most flights, by the time you get to the airport, spend two hours checking in, going through security, and waiting, then flight time, getting off, finding ground trans, and getting into town, will take 5 or 6 hours. With a night train, most of the time used is time you would have spent in your hotel room.