How much do each of them earn with endorsements? Dak gets around $7M/year from endorsements according to rumor. And those endorsements are only because he is the Cowboys' QB. If Dak goes elsewhere, those endorsements do not follow.
If Dak signed for $28M/year it would really be around $35M/year with the built-in endorsements that come along with being QB of the Cowboys.
Also, taxes are lower in Dallas and the power of a dollar is higher in Dallas than LA, Seattle, and Philly. In Pgh the taxes are some of the highest in the country and the city plain blows chunks. Living in GB would absolutely suck. One has to factor in what your money can buy when choosing a city.
It is all about take-home pay and quality of life in the city where you work and your work atmosphere. Dallas is pretty much near the top in all the things that matter most.