Rugby is not the only sport in the news right now. In the US the NBA lockout is big news. Here is an interview with University of Chicago professor of economics Kevin Murphy about the lockout. Here's an interesting point about the relationship between salaries and the number of wins in a season.
NBA.com: One effect of equalizing payrolls is you incentivize good players to go where the money is available. But another might be paying good money to players who might not deserve it, just because more franchises have to spend on … somebody.
KM: That’s a problem. The other thing is, there is some relationship between pay and success but it’s not nearly as strong as people think it is. Even if you were to completely equalize pay across teams, there still would be an enormous variation in strength of teams. In a statistical sense, the level of payroll of a team explains somewhere like 5 percent to 10 percent in the variation in outcomes.
NBA.com: That’s all?
KM: That’s it. I did a little experiment. All you have to do is take the overall distribution of win-loss percentages. Let them tell you what they think the relationship between salaries and wins is. They tell you ‘This much spending is worth this many wins.’ So then you take everybody’s salary down to the mean or up to the mean. Then if you tell me you get an extra win for every $3 million you spend, I’m going to give everyone I’m moving up an extra win for each $3 million. Everybody I move down, I’m going to give one fewer win for each $3 million.
KM: The relationship between salaries and the number of wins in a season is positive, but it’s pretty weak. It certainly is not going to have a dramatic change in the distribution of outcomes. It might change who the winners are and who the losers are, but you’re still going to have some teams that are much better than others. Because some people spend their money much more wisely than others do.