I think no other club would have given Mbappe the number of opportunities PSG management has given him. And that's why Mbappe has been interested in joining Madrid every season, but he ended up signing a contract extension with PSG. PSG paid a lot of money for Mbappe. But teams like Madrid or Manchester United are ready to spend this amount of money. But they won't let Mbappe interfere in the club's internal affairs. PSG management, on the other hand, prioritizes Mbappe's opinion on all matters internal to the club. This is why Mbappe is not leaving PSG. It is foolish to think that Mbappe is only at PSG for money.
The salary Mbappe is receiving in PSG with a new contract is insane which he can not find in other clubs. If big clubs keep raising their salary ceilings, soon we will see massive collapses in finance from them. I do think they know about risk they are facing with if they join the insane salary race.
Mbappe if want to join another big club, he will have to sacrifice his salary and accept a lower salary. He has to choose between winning trophies, personal awards rather than receiving highest salary. Honestly, at PSG level, they are already in a top range in Europe but to win trophies, awards, Real Madrid is a better choice for Mbappe. Beyond Real Madrid, I can not find another good club for him.
But one risk factor, the long time President of Real Madrid Florentino Perez is already too old and that club can have big change in upper structure any time. That can put Real Madrid in a few years of crisis if it happens.