No one is disputing that their five children should be looked after and supported. However, money for this should be allocated on the basis of their need rather than Elon Musk's ability to pay, and I'm not sure how one could spend more than a couple of million per child.
In fact, beyond a certain point I'd suggest that having lots of money is probably a negative influence in a child's life.
Conceiving and caring for five kids has a pretty huge opportunity cost. In addition, her staying home and taking care of the kids meant that he had more time to dedicate to earning money. The conventional wisdom of divorce proceedings is that a mother should be compensated for both that opportunity cost and get a cut for helping her husband free up time to dedicate to work, as well as the actual maintenance costs of raising the kids.
In fact, beyond a certain point I'd suggest that having lots of money is probably a negative influence in a child's life.