Picture this. You are given forty thousand dollars to invest in stocks, pretty neat right? Not only that, but you have millions of adoring fans, and their emotions ride and fall on your every investment...liking the sound of this? Only downside, your rival from across the street is given two hundred and forty thousand dollars to purchase the same stocks you had hoped to, darn! This sounds like a fictional scenario, but add a few zeroes, and you have Major League Baseball, the only major sport without a salary cap.
Is the salary cap needed though? Look at the 2008 MLB season...the Yankees payroll was over two hundred million dollars! The lowest, belonging to the hapless Florida Marlins was a microscopic twenty one million. Yankees third basemen Alex Rodriguez's salary alone was higher then the Marlins. You say money can't buy success, and point out last season as an example. The teams with the three largest payrolls (Yankees, Tigers, Mets) did not make the playoffs. The two teams who faced off in the World Series, the Rays and the Phillies had the 29th and 13th largest payrolls respectively.
But let's look at the big picture..where each team placed in their division compared to their salary. The following list is of 2008 MLB team salaries, the highest being at the top, the second number is where they placed in their division. I've also marked which teams qualified for the playoffs.
1. New York Yankees (3rd)
2. Detroit Tigers (Last)
3. New York Mets (2nd)
4. Boston Red Sox (2nd) Playoffs
5. Chicago White Sox (1st) Playoffs
6. Los Angelas Angels (1st) Playoffs
7. Chicago Cubs (1st) Playoffs
8. Los Angelas Dodgers (1st) Playoffs
9. Seattle Mariners (Last)
10. Atlanta Braves (4th)
11. St. Louis Cardinals (4th)
12. Toronto Blue Jays (4th)
13. Philadelphia Phillies (1st) Playoffs
14. Houston Astros (3rd)
15. Milwaukee Brewers (2nd) Playoffs
16. Cleveland Indians (3rd)
17. San Francisco Giants (4th)
18. Cincinnati Reds (5th)
19. San Diego Padres (Last)
20. Colorado Rockies (3rd)
21. Texas Rangers (2nd)
22. Baltimore Orioles (Last)
23. Arizona Diamondbacks (2nd)
24. Minnesota Twins (2nd)
25. Kansas City Royals (4th)
26. Washington Nationals (Last)
27. Pittsburgh Pirates (Last)
28. Oakland Athletics (3rd)
29. Tampa Bay Rays (1st) Playoffs
30. Florida Marlins (3rd)

Every single team that qualified for the playoffs, with the exception of the cinderalla Rays, was in the top half of the league's top payrolls. Five of the seven division champions were in the top ten highest payrolls. Money may not be able to buy championships, but it sure can buy a playoff spot.