CEO pay is = their "replace-ability" costs.
There are only a handful of people in the world capable of running a state or running a massive corporation. There are hundreds of millions of people that can be trained in a month or less to do most jobs in the USA. That is why the CEO makes 500 or 600 times. They have a unique set of skills, experiences, relationships, networks, and creativity required to run a ship worth billions and thousands of employees.
Lebron james makes $250,000 per game, and will be near $400,000 PER GAME after the new 2016 TV contract... and he's worth every cent, thanks to the tickets/TV sales/shoe/jerseys, etc. You can't just "replace" a lebron - unique blend of talent, marketability, long-term durability, etc.