There are 2 ways to look at it, as I see it:
1) Whatever Brady wants, he's earned
2) None of these columnists have any idea what they're talking about. "He took a discount last time, so naturally he's going to want a huge payday now" might be most backwards rationale I've heard yet for why he'll inevitably want a huge payout.
Personally, I'm not worrying about it at all. Whatever he costs will be money well spent, and I think he knows better than to go into the realm of absurdity (which would just mean that he'd have an inferior supporting cast helping to win more SBs). And Giselle makes like $30M per year, so they're not exactly hurting for money either.