A high salary is apparently not as valuable to him as playing for the club he has dreamed of since childhood. The fact that they are treating him like this now I think will only make it worse for the team, because in the Champions League without him it will be very difficult for them, unlike in the French league. If they make it out of the group stage, they are unlikely to go far without him
Do you know what the reason is for Mbappe to more or less boycott everything? It is not PSG, it is Mbappe who wants the massive bonus for the new season while he wants to leave the club at the same time. But you have to understand that this is a bonus he would get when he stays. His plan is to get PSG to pay him his bonus and also to let him go because otherwise they would lose the total transfer fee if he stays another year. That is his calculation. If Real goes up with the price, PSG could take a chunk of that money and also pay him a bonus he never deserved. Maybe it is not as idealistic as you think as if he just wants to go to the club he has been dreaming of since his childhood but now his bosses destroy his dream.
Yes, Mbappe is obviously a cynic, and all the fairy tales in 2023 about "my favorite club since childhood, etc." it's not even funny anymore. But he is in his right, he fulfills the contract and there can be no claims against him. PSG is another matter - they paid him for something, but they are trying to pressure him to get more from him than he was obliged to do. This is both unethical and somewhat illegal.