I think they are grossly overpaid, but since you need some points i'll give you some. You could argue that since they retire at such a young age the money they get while playing is sort of a pension ( Not sure if they already get one through the league they are in though so you should look into that). They are basically away from their family for the entire span of the season. They become a public figure. So, nearly every facet of their life is publicized, or at least with the super stars. I mean look at Kobe, Ben Rothlisberger (sp?), and Tiger. They do work incredibly hard at what they do, and people are willing the pay insane amounts of money to watch them play. Fans give them unreal amounts of shit while they are and aren't playing. Due to their contract they are very limited in the kinds of activities they do in the off season.
Not very good points, but I hope they help you out.