I agree, there must be a trade fair going on so it is not an issue whether this hotel is worth 315 Euro but whether or not you will get any cheapish hotel room in Munich. I am there quite frequently. A rate of about 170 Euro is pretty normal, the best one I had was 99 incl. of breakfast. Check for your dates on www.hrs.de and you will get an overview of hotel rates that specific night (and if they have LM available with some certainty a BRG claim).