Munich is not a cheap city. Bavaria is quite affluent, and Munich, the region's capital, isn't bargain-friendly by any stretch of the imagination. From the moment you contemplate taking a taxi into town from the airport (and wisely decide to take the train or S-Bahn instead), you'll be struck by the high general living cost index.
Munich Hotel Overview
That said, Munich's midrange and budget hotel offerings include plenty of decent deals. The massive hotel rate inflation that you see in Rome, for example, is not to be found in Munich. Even Munich's first tier of boutique hotels (none of which, obviously, make our listings here) are notoriously reasonable.
Many of Munich's less expensive hotels are located quite close to the Hauptbahnhof, or main train station. In particular, the area to the south of the main train station is littered with hotels. It's kind of bewildering how many hotels and hostels there are to be found here.
For €90 in high season (barring Oktoberfest) you will be able to nab a very average double room to the north or south of the train station. For €150, you can have yourself a hotel with all the top-notch business hotel accoutrements.
The most important thing to know is that Munich's hotel rates shoot to the stratosphere during Oktoberfest. In some cases, nightly rates triple. If you visit Munich during Oktoberfest, consider staying in a nearby city (even as far away as Rosenheim or Freising) and taking the train in to Munich. You'll save quite a bit.