Over nearly two decades, no player has dominated the NFL like New England Patriots quarterback Tom Brady

There are a lot of keys to his success, of course, and lots of reasons why he's been able to overcome long odds and make his 9th Super Bowl appearance this weekend. 

There's his health regimen, his unique way of forging relationships with new players, and his legendary drive and determination. There's also the simple fact that he's been willing to study the game and adapt the way he plays it as he's grown older and his natural athleticism has succumbed a bit to time.

However, there's also a very quantifiable thing that he's done: he's been willing to make financial sacrifices to achieve something greater.

Over the course of his NFL career, Brady has earned about $197 million. But he's not the highest paid player in the league by a long shot -- even though he quite likely could have been if that had been his main priority.

Instead, according to an analysis by Business Insider, he's given up at least $60 million, potentially closer to $100 million, by being willing to sign smaller contracts than the market would seem to bear. 

As benchmarks, Business Insider compared the contracts Brady signed to those signed by other top quarterbacks at different times in his career, when he would have been able to negotiate more.

Among them: Peyton Manning, Eli Manning, Drew Brees, and Ben Roethlisberger. It adds up to at least $60 million.

So why do it? To win -- because being willing to accept smaller contracts meant the Patriots had room under the salary cap to sign other players, who in turn made further success more likely.

As an example, in 2007, Bray restructured his contract so the Patriots could afford wide receiver Randy Moss. Brady and Moss were an amazing combination, and their team went undefeated in the regular season (although we do have to acknowledge that it didn't quite work out in the end, as they lost the Super Bowl).

It's not the only example; in recent years, he's also signed contracts with less upfront money so that the Patriots could sign and resign free agents. 

This isn't an exact science of course. There are other things that go into negotiating contracts. And it's also quite possible that without that cadre of talented players around him, Brady would have had a very different career.

He might not still be playing, and certainly might not be on the cusp of starting his ninth Super Bowl (and hoping for a sixth win). 

It's also true that Brady is married to Giselle Bunchen, who is one of the highest earning women in the entertainment industry. So it's not as if their family is exactly hurting for money.

Still, it's worth noting that to win, Brady was willing to sacrifice dollars now for the chance of greater glory later. It could well be the difference between being the greatest of all time -- and simply the highest-paid.