Well, as I stated earlier, it is not for any one person to decide what a CEO is worth; it's up to the marketplace. Let's say, for example, all the Fortune 500 companies' CEO's demand a 50% pay raise together in a coordinated effort (basically, lets pretend a company is stuck with their current CEO and are forced to pay him whatever he wishes). So, now let's look at one individual company, for example McDonald's. McDonald's, because of this extremely illicit and illegal agreement between top CEO's everywhere, is forced to pay their existing CEO the 50% raise, because (again, redonkulous scenario, but roll with me here) they cannot replace their CEO, which effectively means the supply of CEO's is one, or in other words, the current CEO holds a monopoly upon th e CEO position at McDonalds. The supply of this CEO, being in this (admittedly asinine) example nearly zero, translates into a relatively high demand for him to not quit his job and leave McDonalds CEO-less. Thus, McDonald's pays him what he asks because McDonald's doesn't have a choice.
Now, in themreal marketplace, lets say Mr. McDonald's CEO demands the same 50% pay raise or threatens to quit as in the previous scenario. However, this time, McDkonalds has the option to either: keep the CEO with the raise, or go find a new CEO for (presumanly) less cost than the current CEO with his demanded raise. Lets say they ditch the old CEO and go with new blood for their next CEO, paying this new dude the same amount that they paid their old CEO. Here, McDonald's decided that the new CEO provided the company with a higher wealth creating potential than the prior CEO did. Because the supply of able and willing CEO's was higher in this scenario, demand for the existing CEO was lowered as a result, meaning McDonalds now isn't forced into paying him his demanded raise.
This is basically how salaries are determined for positions of all natures in all industries in the private sector. It's a balancing act between two factors: the supply of people willing and able to fill a position for X pay, and the demand for people to fill a position at X pay. This equation is very easily modeled in graphical form, so here is a supply and demand curve for you to gander at:
http://www.geopolitics.us/wp-content...mand-Graph.png
It states that there will always be an optimal point somewhere where the two curves intersect. This point decided the current salary of the average employee of any given profession in the private sector.