Atherton is almost defined as a community for the ultra-rich, what with its prohibition on multi-family housing and enforcement of a minimal ratio of house floor area to lot size.
It's not "catching up," it was built for and by business elites. For example, Los Altos Hills incorporated specifically to avoid raising taxes or building any kind of civic infrastructure. Saratoga has dispensed with its police department. None of these places are even remotely affordable (or reachable without a car), and they have never been.