It absolutely is ridiculous by any standards, especially because at this price point you're really putting all of your money on performance based on 6 months of work. When you see world-record fees there usually always is a marketing aspect brought into the value of the deal. In this case, Mbappe is still not a world-renowned name.....he's getting there but based on rumors of a world-record deal more than on his performances at this point and he's not going to bring marketing revenue like a player of that price would without confirming his potential in a superior league. I absolutely believe he will, but what the hell do I know? It's still a gamble!
I've heard rumors left and right, but I'm not sure Monaco actually has received a single concrete offer that would be world-breaking, because I struggle to understand how they could turn that down given the historic profit they could make off a kid they only got 6 months out of without spending much of anything to get him to play for them. Even if Madrid sell Morata, I don't think it means Mbappe is automatically going to Madrid. He's moving to be a starter and that's complicated to offer for Madrid or any club that could afford the fee not named PSG (which Monaco is not interested in strengthening).