MLB does not have a salary cap. Teams can spend as much as they want on salaries for players. It is not uncommon, then, to hear people complain that baseball lacks parity and that high salary teams buy championships.
I think this claim is wrong, but because of time constraints, I can't argue for it in this post. Nevertheless, I think the following suggests that we ought to question this linkage between high salaries and team performance.
The following lists the top ten salary spenders for 2010 (according to http://www.benfry.com/salaryper/ ):
4. Chicago Cubs
7. Chicago White Sox
Only 4 of these teams made the playoffs: the Yankees, Phillies, Giants, and Twins.
The same pattern held in 2009:
Top Ten Salaries
4. Red Sox
Only 5 of these teams made the playoffs in 2009: Yankees, Red Sox, Angeles, Phillies, and Dodgers.
This is far from definitive, but it is suggestive that there is much more to fielding a successful team than paying high salaries.