My reading of this is that teams like the Braves are learning not to differentiate between arbitration salaries and free agent salaries. This way, they get Freeman, who will probably continue to be a solidly above-average player, through what will most likely be his prime. This extension won't run out until he is 32, then they can let him leave. When he hits the open market again, some foolish team can overpay him for his declining years, like the Angels are doing with Pujols and the Mariners will do with Cano. It's all the same money, so why not use it to pay for a player's true peak/superstar years, then let him become someone else's problem.
This is what a mid-market team like the Braves can afford to do. The A's and Rays aren't really wealthy enough to sign players to any major extensions, but most other teams can. Pujols is a great example. His first extension ran 8 years, and in those 8 years, he made $116 million while producing 60.7 WAR (per
Fangraphs). The Cardinals paid less than $2 million per WAR. The Angels, on the other hand, are on pace to pay almost $11 million per WAR. (Yes, that includes his mostly injured 2013, but that's balanced out by the presumption of Pujols' continual decline.) I know inflation has gone crazy over the last few years, but really, even if the Cardinals had doubled the AAV of that extension, they still clearly come out ahead in terms of value.
I think we're going to see more of this. Teams saying, "Let's forget about what arbitration years are 'supposed' to cost. Let's buy out the prime years of a solid player, then let some other team overpay for their decline."