PSG will not sell him for 180 M +/- this summer. At this price, they would rather keep him than make no profit on a player that has grown on and off the field.
This policy is maybe a mistake since the club almost always sells (or don't sell at all) at a loss by keeping the players to the very end : even Cavani who has become not needed was not sold this summer or this winter and will go out on the free this summer.
I think he will go to Madrid for more than 200 M. They are not shy to dumb (edit : dump) big money and they have been grooming him for a long time.
But i agree with the guy who is saying Mbappé is not the GOAT either. He is an exceptional player but marginally inferior to Neymar in his own team, let alone Messi.