you're damn right, they don't get credit, but the average salary of a regular TV writer (ie.. the writers on your favorite shows, and those who benefit the most from all of this, because an unemployed writer earns nothing) is around $200,000.
So, yeah, some hack actors get paid millions for the same or less work, but that's the thing -- nobody is going to watch a sitcom because it was written by Steven J. Finnegan... but they WILL watch it because it stars that dude from Friends. At least that is the theory.
It works the same with pro sports. The GM gets paid a fraction of what ARod or Roger Clemens earn, but has as much, if not more impact on the team's success. Billy Bean, however, doesn't put asses in seats on the power of his name. Barry Bonds does.