Still strange
reverting to the initial question, there is still something that strikes me:
MUC-SKG-MUC direct routing on Aegean or Olympic will indeed give you a paid ticket price in the neighbourhood of 170-200€ incl taxes. Taxes actually amount to €29.35 on this routing:
Tax:German Passenger Service Charge €10.85
Tax:German Airport Security Tax €6.50
Tax:Greek Airport Development Charge €12.00
The Miles&More routing through VIE on OS has taxes of €73.95:
Tax:German Passenger Service Charge €10.85
Tax:German Airport Security Tax €6.50
Tax:Greek Airport Development Charge €12.00
Tax:Austrian Passenger Security Charge €16.00
Tax:Austrian Passenger Service Charge €28.34
While I agree that €75 is still a lot compared to the paid ticket fare, I can't see where the €112 are coming from.