I think pay is largely a matter of power. Even bad managers get paid well. CEOs that drive their company to bankruptcy often still get massive bonuses on the way out. There are lots of people who want to do that job, and the people doing it aren't always good at it, yet still get paid a ton.

The worst paid are always the most powerless.

Of course having rare skills that are in high demand also gives you power, but it's one of many kinds of power that can give you more control over your own salary.