It seems that List was actually saying "highest paid in 2016" which, eh, maybe. But the idea that he'd be the 7th highest paid athlete in a world that includes soccer players, Formula 1 drivers, baseball players and NBA players making 30 million per, seems dubious to me.
Just in the NFC South, believe he has a smaller base contract than Rodgers, Brees and Ryan, and he would likely have less overall wealth than Julius Peppers and Adrian Peterson if they've saved any of their money from a decade in the league (no personal life judgments!). His guarantee was something like $60 million (I think) but he's in the third year of that deal, meaning he's received about half that.
It's not like Newton has a big national ad campaign that would make up the difference between him and Ronaldo, Federer, LeBron, Rodgers, Curry, etc.