I've always thought it was much easier to "buy a championship" in the NBA than in the other leagues.
How many years did the Yanks have the top payroll and kept getting eliminated in the playoffs? Sure, their big spending in the last 15 years has resulted in multiple championships, but you can't really "buy the championship" in baseball (or football or hockey) like you can in the NBA. In the NBA, if you can "buy" 2 or 3 really great players, you will most likely be one of the last 4 teams standing - and you have a pretty good shot of winning it all.
-Shaq being brought to L.A. to accompany a young Kobe
-Pau being virtually stolen to help Kobe
-Pierce, Garnett, Allen = 2 huge free agents teaming up with Pierce to win a championship
-Lebron/Wade/Bosh = I really don't expect this to be any different. They will have success. Especially with the signings they've made in recent days (Miller, probably Ilgauskus who is decent, etc.)
There have been some epic flops though, namely the Kobe/Shaq/Malone/Payton experience. 4 Hall of Famers and they couldn't win it. But, Malone and Payton were no longer spring chickens.
If you do that in the other leagues, you may win it all, but there's a good chance you still won't. In the NBA, you will at least get deep into the playoffs - that's pretty much guaranteed.