The real question is, does a CEO making $30,000,000 bring an extra $25,000,000 worth of value to his or her company over a CEO who only makes $5,000,000?
Having met a fair number of CEOs of companies of all different sizes, the answer, usually, is: no. Most high-end CEOs don't add value to their companies that comes anywhere close to their compensation.
The massive paycheck of a Fortune 500 CEO can be compared to the money earned by losing a championship boxing match. Yes, any of us can stand in a ring and be beaten senseless in return for a few million dollars; the hard part is getting the right to stand in that ring. Did the human punching bag "earn" his cut? Not in that particular fight, no. But his loser's take is a payoff for actually earning the chance to be there.
A fair number of people could competently manage a large corporation, and would do it for less than $30,000,000; however, there can only be 500 Fortune 500 CEOs at any time, and the hard part is joining the club. The CEO does not "deserve" that giant paycheck; he or she does nothing to justify it; his or he skills are not six times greater that those of the CEO of a smaller company who "merely" makes $5,000,000 a year. Nonetheless, that Fortune 500 CEO is being rewarded for finally having joined the club.