Have you heard about the law of supply and demand? Because it is bullshit. Salaries are not set based upon some fictional law of economics. Instead, look to sociology and biology to explain managerial salaries. Developers may be harder to recruit than managers but occupy a lower rung on the totem pole than them. Hence cannot be paid more than managers. Because pay is status and leaders have more status than followers. The more people you lead the more status and money.