I don't see why the cost of a nanny is an elephant in the room? Surely at least one reason rich people hire a nanny is the convenience of having individual childcare who don't stop at 6pm sharp and can travel with you?
That aside, I am less interested in the childcare choices of the wealthy and more interested in why so much effort goes in to keeping the world of children and work so separate.
Some is due to quite reasonable legislation to protect young children from exploitation. But the sheer outrage and horror on some threads about women taking their babies in to work is more than practicality - it is enforcing a cultural norm that children should remain separated from the world of work. Who benefits from the strength of that prohibition?