I know but any number you pick that isn’t 50% will be arbitrary. 50% means they are equal but anything other than that is arbitrary. How would you pick a numbers 40%? 30%? There is no objective way to quantify that. There is no mathematical formula. So let them negotiate instead.

And I said before that they should be able to leave the “marriage” any time if they feel mistreated. That also means they can renegotiate the terms of their agreement any time too. She can ask for more money or he can choose to give her less as his wealth grows. If they don’t agree then they can always go their separate ways.

If they agreed to do 40% for example, and he became a multimillionaire and said that he is only willing to give her 20% now, that is still a good deal for her. She is getting way more money than she was before without providing any additional value. But if she isn’t happy with 20% then she can leave the relationship. Your greatest negotiating power in a relationship comes from the ability to leave the relationship. Marriage basically castrates a man because it takes that away from him.