It doesn’t matter that the effect of that is to make him more likely to divorce her to get out of paying it.
It certainly does matter halachicly. Even all the rabbinic supporters of the prenup admit that if you change the dollar amount in the prenup to $500/day (or any amount more than the obligatory mezonos) and leave everything else in the prenup exactly as is, it halachicly invalidates the prenup.
Because if you say that, then the whole kesuba is one giant get-meuseh generator, because he has to pay mezonos until they’re divorced!
Mezonos is not equal to $150/day, $55,000/year, to support one person (plus inflation and plus giving her her employment income.)