CEOs and top executives are highly replaceable too (they sure change companies a lot), and yet they command massive salaries. What happened to the laws of supply and demand there? Why do CEOs have to die or retire before the board decides to replace them with someone more competent? How was Steve Ballmer able to stay in charge at Microsoft for so long?? I remember the day Ballmer announced his resignation, MSFT stock went up by like 10%! So the market definitely wanted him out!
The main difference is that executives have leverage (and they have friends in high places) while average employees have almost no leverage.
It's the government's job to make sure that employees have some sort of leverage over their employers.
There's supply and demand, and then there's also principal agent problems. In practice, shareholder capitalism is a lie: companies are run for the benefits of upper management.
It's not only rank-and-file employees that have little leverage, average shareholders aren't much better off.
The government can try and make sure to keep barriers to entry low for competitors, and barriers to switching to competitors for employees. Competition keeps companies in line, even when it's executives running the show.
The main difference is that executives have leverage (and they have friends in high places) while average employees have almost no leverage.
It's the government's job to make sure that employees have some sort of leverage over their employers.