Bayern has never put too much money on any of their players and I don't think they will make an exception for Sane, no matter how great player he is.
Things are changing and so is Bayern. They will have to if they want to stay competitive and on top. Maybe you are forgetting that Bayern bought Hernandez last summer for €80 million and Pavard for €35 million. Both players are defenders.
The Covid-19 pandemic will surely slow down the crazy transfer spending, otherwise we would see the same by many clubs.