There is the argument that pro athletes earn this money for their sponsored companies, so they deserve these pay offs. Pro football players, basketball, baseball, golf, hockey.
There are downsides however. That is alot of money to be paying a relatively small portion of the population. This is inherently bad for the economy. Is it offset by the earningings of their sponsors? I suppose. But this is not really an increase in spending caused by the fame of these athletes, its simply shifting the spending. If he hadn't been so popular that you never bought those 2 dozen pairs of Air Jordan shoes over the years, its true Nike wouldn't have earned that money, but you would have spent it elsewhere. In other words, these athletes dont generate spending, they dont create wealth, they simply shift it.
You also wouldn't pay nearly as much for the exact same shoes if Jordan hadn't become so popular. Demand increases, prices generally go up. Artificial costs generated, wealth shifted from the individuals to the corporations. Is this good for the economy?
Finally, the social impact. Kids grow up seeing pro athletes as some of the greatest earning potentials out there, see the fame and everything that goes with it... they are obvious role models. Gone are the days when you'd ask a young child what he wants to be, and he responds with a fireman or an engineer. By far the most common answer will be pro baseball player, or basketball player, etc. Why not? Its a seemingly great life, unbelievable pay, hell I wish I was one too. But the sad truth is only a smll fraction of 1 percent of kids will ever be able to make that dream a reality. So we get a bunch of college students with football a their number one priority rather than studies, professional athletes that can barely string 2 coherent sentences together, and everyone else wanting to get in on the action. This, again, cannot be good for the economy, or society.
The alternate argument would be this sort of wealth is the motivation that drives captialism. If you take the incentive away, or place a cap on it, this could also hurt the economy as a whole. There is no black and white answer.