Great Question. Should salaries of any celebrity be justified! If we not, we would be in a socialistic, if not communistic country. Sports person are paid those fees because they worked hard to building up a profile of perceived value. In the end, teams want to win because money is at stake and thus will take on a player that will help them achieve that.
Needless to say, while there are high paid athletes in the world, these numbers are minimal to the amount of athletes to the world. We are only made aware of these high paid athletes because they have a good marketing manager. Other athletes contribute years in sports without being paid a cent. Unfortunately it is just - as they say - 'how the cookie crumbles'!