"Oh, those guys all make way too much money for playing some stupid game. No job is worth $20 million dollars per year."
This sentiment can be interpreted one of two ways. On the one hand are the people who think professional athletes just make too much money on the whole. While the sentiment of this statement is accurate (the US economy and society would likely be extremely similar if pro sports didn't exist), athletics on the professional level are a business, and the fact remains that people will pay a lot of money to see games. The linked article indicates that the Dallas Cowboys were worth a cool $1.81 BILLION dollars in 2013, roughly the annual GDP of San Marino. OK, that doesn't sound too impressive, but rest assured there is serious money changing hands in all major American leagues.
The second argument is that while the league may be appropriately valued, superstars in these leagues make way too much money. After all, there are only about 400 NBA players at any one time, so they already represent the top .0001% of basketball players in America, let alone worldwide. However, within these 400 players, some clearly bring a lot more value than others, and are in fact deserving of extremely massive salaries. Yes, friends, Lebron James (and his $16 million salary) is woefully underpaid.
