Yeah that sounds fantastic. Except that contract runs until he is 41.
It's possible he'll still be playing at 41 but he won't be worth $20 million a year anymore and, odds are, he won't be playing then.
This isn't a tremendous sacrifice on Brady's part, this is a cap move the Patriots will have to pay for eventually. But they are correctly estimating that they'll suck anyways the year Brady retires, so just pay all the bills then.
The Saints should do the same thing.