Brussels and Zurich airports are quite close to the city which gives you more options of places to stay at a more reasonable cost and a quick train ride to the airport. I believe MUC airport is much further to the city - only time I overnighted there was in 2021 and I stayed at the Novotel that was 1-2 stops away on the bus (I think it was bus 350)
Mr E - what hotel are you referencing at IST - I’ve only ever checked the Yotel and I’ve always seen prices in excess of 300-350 euros. I just passed through IST yesterday but managed to snag a sleeping room in the TK business lounge since my connection was only about 7 hours