Find a CEO whose motivation is more "make the world a better place" than "make millions of dollars a year". $500k is a large enough salary to live well just about anywhere. After that it's just "victory points" in the game of careerism.
These theories are untested, except that we now know for certain that paying $2.5M doesn't guarantee that the CEO is any good.
I would bet you can hire an excellent, technically competent CEO for Mozilla for $250k a year.
But how long would they stay after other companies learn this new person is actually competent and start throwing money at them.
And Mozilla's poor track record suggests that if Mozilla insists on paying the same CEO salary, they might do well to find a different CEO to give it to.
I think the point is less that this CEO should take a pay cut — although she probably should — but more that the mediocrity + layoffs + exorbitant-CEO-salary situation here reeks of self-dealing.