If you don't think eventually we'll be priced out for top talent then sure, let the sports washers spend whatever they want. Or do you think that people would just turn down double or triple the money consistently? If so then you have more faith in humanity than I do.
As far as going to Madrid, they're just a good team nothing great. If you think just adding Mbappe would make them unassailable then there's probably nothing more anybody could say to you that would matter.
Mbappe going to Real Madrid would have seen him combined with 2 other very talented young attackers in Vinicius and Rodrygo. They do have the pull and the finances, so they could also add Tchouameni to Camavinga and Valverde, and suddenly you have a very talented and very young front 6.
Their entire strategy of not spending on players over the last 2-3 years was based on 2 main targets: 1. Upgrading the stadium and 2. Getting Mbappe. With Mbappe staying at PSG, Real Madrid will have to look for a new plan.
Like I have said, they are true rivals for us. The likes of PSG and Man City are irrelevant for us in the big picture ...