Mbappe didn't even need money but he needs to achieve more achievements as many as possible. He never got what he wanted in PSG. This is also the main reason why he was also thinking to leave from PSG instead of stay even longer in the club. Mbappe had no choice other than leave from PSG to develop himself as a great player in this decade. In fact, many people are always supporting him no matter where he will be playing with. Mbapp needs to focus in increasing his experience and quality as a great footballers.
Mbappe has won world cup but he never won UCL trophy. Leaving from PSG will give him the right place to get trophy. I hope he will understand it and try to think about leaving from PSG to join in another club like real madrid.
That is why he is not at all interested in offers from one of the clubs in the Saudi pro league even though he could set a new record with the most expensive transfer which might be difficult to break but as you said he is not after money because in fact he already got it at PSG, but he is hoping for it. a more prestigious title that seems difficult to get if he is still at PSG, so there are rumors that he has made a personal agreement with Real Madrid if his contract ends at the Parisian club.
So if PSG can't convince him to extend his contract and also if this season there are no achievements achieved by PSG in European competitions then there is a big chance of seeing him leave Ligue 1 to play in a different league with a club that can make his dream come true, Real Madrid is one of them or it could be that he will go to the English Premier League because in this league there is also a club that is quite strong in the Champions League.
Every superstar palyer usually pays more attention to earning more money because they are playing where they don't get enough salary or because they are not in the good financial station but for a player like Mbappe Mbappe the station is not the same as other players because we know PSG can even offer him more money and he is financially satisfied that's why Mbappe wants to play in another team where he can earn more achievements instead of money and that's why he prefers to play in a team like Real Madrid.