NFL Piles of Cash to Retire?

I know everyone is completely sick of the Brett Favre situation and I said I wasn't going to talk about it, and then I did anyway, but I just want to touch on one singular topic and bust out a theoretical. In order to get Favre to stay in Mississippi, the Packers offered him 20 million to stay retired. The single question that came to my mind is how the hell could the NFL allow this. Shouldn't the NFL be about paying people to play and not paying people no to play. And then here comes the theoretical.Say coming the AFC clearly identified the Pats as the divisional front runner. Now inarguably the key player to the Patriots is Tom Brady. He's probably their best player but simply put their most irreplaceable player. His backups are Matt Cassell and Matt Gutierrez both of whom could not start at Michigan or USC back in their school days. So, if it was ever legal for the Packers to offer 20 million to Favre to stay retired, why would it not be legal for the AFC tea...