With the train construction, the cost being €27,50 to get to the center.
Yes, April, where did you get that €27,50 cost? An MVV ticket from the airport into downtown Munich (using zones M, 1-5) is 13€. Using the designated bus replacements doesn't change that.
A single ticket on the LH express bus to Munich central station is
11,50€, for example.
The problem with using the LH express bus is that it only goes to the Hbf (or Nordfriedhof, but I don't think that's really where you want to go), then you have to pay extra to take other form of transit from there. But with a 13€ MVV M-5 ticket, you can go to any transit stop, S- or U-Bahn station, tram stop, or bus stop) in the central, M, zone. If you hotel is near Marienplatz, for instance, you can go to that station.