Simple.

Let individuals decide how much they want to spend for their women (or men?) and children.

If a billionaire want to spend $100 million for 10 kids, it’s his right. If he wants to spend “only” $1 million or $100k for each kid, and produce 1000 kids instead, it’s also his right as long as the future mom also agree. Let the parents decide.

If government has a say it should be some minimal amount applicable equally to everyone or adjusted by kids’ need. Parents’ financial capability is irrelevant.