There are a couple of cheap flight operators that fly from/to Germany. One is
air berlin and the other is German Wings (I don't know this URL but I'm sure a google will quickly bring it up). So long as you make sure to book well in advance you may be able to find a cheap flight for say 40 Euros. Another suggestion is to use Easyjet or Ryanair - you may have to use 2 flights (eg fly to Stansted UK and then fly to Germany) but if you have really cheap flights (20 Euros or less each trip) it can still prove economical. Even this way will be quicker than the bus!