One should be aware of that its a lot of comparing apples with oranges when it comes to salaries being reported. Spanish media likes to report net salaries focusing on how much the player is pocketing while English media likes to focus on the total cost for the club.
Then you have countries like France and my homeland Sweden where the gross salary is not the only cost for the club, but there is also a payroll tax around 30 percent or so (In Sweden its 32 percent). Which means that a Neymar who makes (just as an example) 500k gross a week, costs PSG maybe 650k or so including payroll tax per week, but no one reports anything but the gross salary. Which is what you pay income tax on. In Sweden at least, I should not speak for the French but I think its the same.
What I can say with pretty big certainty is that it will cost PSG more to offer De Ligt a gross salary of 250k a week than it will United.
In addition to this you have all of the incentives, etc, which makes it really difficult to say what the wage value of the contract really is.
In the best of worlds UEFA would force its member clubs to be transparent about the wages paid to each individual player and adapt a common principle of declaring wages.