Three years, $91 million fully guaranteed for Kirk Cousins is a stretch

Not sure that I caught a whole lot of breakdown there.
$91M over 3 years comes out to $30.33 per year.  That is about a 10% increase over Garappolo's $27.5M annual average.  Is that a lot?  Maybe. The breakdown says it is more than 28, 28.5, 29, 29.5, and 30.  This is undeniably true. But does that make a 10% jump implausible? 
The breakdown also says it is implausible because there is no way the Jets would pay that much and they would have to pay more than the Vikings. But how do we know the Jets won't pay that much?
Then there is the point that the Vikings are not ones to spend crazy money and recognize they need to sign other great players and would want more than a 3-year deal.  All true and probably the most compelling arguments. But there may be ways to sign all or most of our guys and still make a $30M QB salary fit, especially if you think he can get this team to the SB and you see the salary cap continue to increase by $10M+ in the coming years.
I am not advocating paying Cousins $30.3M a year or guaranteeing him $91M over 3 years, I'm just not entirely convinced that it is not going to happen.