When I looked at the dataset provided by Nathan I first wondered what was missing. Quite a few stars were missing in the list. I added Simon Baker whose Mentalist gets a huge audience and who is said to be getting $450k per show. Others who probably should be there include Forest Whittaker for the Criminal Minds spinoff, Jim Belushi in the Defenders, Kate Walsh in Private Practice or Elizabeth Michell in V. I don't think any of them is settling for less than $15k per episode.
Another thing were the audiences. There are a few good sources for that (and some less good) so I tried to approximate how much viewers a show would generate for their channel. I came up with hourly viewers because a show that brings 10 million people to one channel for half an hour should be equivalent to one that gets 5 million viewers for an hour, right? In fact, I wanted to come up with a proxy of how much value a TV show was generating and how much of that went into the pockets of the cast. It's probably possible to come up with a precise answer with better data than could be assembled by an amateur over a lunch break, audience is probably a part of the equation, but the short story doesn't require much calculation: actors only get the crumbs of a very fat pie. A show like Grey's Anatomy got $329.1m dollars of ad revenue in 2009, which I assume is an US-only figure, the show being syndicated in many countries, unfortunately including France. And that excludes sales of DVD, paid donwloads and other streams of revenue. Out of that, Patrick Dempsey only got $6m. Now $6m is a lot of money, but actors of successful, established shows don't get a very good deal here. In the last seasons of "Friends", the 6 main actors all got $1m per episode, which seemed fair in retrospect. Sarah Jessica Parker's salary even reached $3.2m per Sex and the City episode, but she was co-producer. And this was then.
The chart can be divided in quadrants. On the lower-right corner, Charlie Sheen, who is the only one there with an old-school deal. On the higher-left corner, the work horses - stars of the crime shows with stellar ratings, who could ask for more. On the very bottom-left, those who are happy to be there. Etc.
Now some stars of shows that get well over 10m viewers get "only" around $100k per episode. So obviously the revenue stream must go somewhere else! my money is on the writers
Also for fun, I computed the ratio of their salary to the length of each episode. I once calculated that I earned about 83 cents a minute, which sounds pretty ridiculous compared to Charlie Sheen's $62500!