I think bringing Mbappe isn't in Real Madrid's capacity but in Mbappe hands and PSG. If Mbappe has made up his mind to come to Madrid and PSG also accepts this,Real Madrid will pay for the transfer Instantly because they have tried their best after the world cup to bring Mbappe to Real Madrid but things didn't work out for them. Let's hope they will succeed to bring him to Real Madrid before next season so that he can add value to the club matches. If I am not mistaken,Real Madrid is the richest club and has all it takes to bring in Mbappe. If PSG feels remorse to let Mbappe go then they will be at lost by the time Mbappe contract is over with them.
In fact, PSG offered Mbappe a very large amount of money to stay at PSG, but all of that is the decision of the player, I'm sure Mbappe will leave PSG because if he stays at PSG then his career will never develop, now Mbappe is in a period of his glory and if he makes the wrong decisions then his football career will never develop.
I also hope that Mbappe will be willing to move to Real Madrid, it will be very good for his career.
And the Real Madrid team are in dire need of a striker to replace the departed Karim Benzema and I think Mbappe is a perfect replacement.