Prescott's agent is going to want the same money or better but it is still all about the guarantee money. Check the numbers on Wentz, cap hit this year is some $8mm, next year $22mm and so forth. It is really a six (6) year deal as he is going into his 4th year and Philly would have took the 5th year option on him.
For Dak, probably means a 5 year deal at around $158mm then add in this year at $720k, you really have $26mm avg per year. Probably $110mm in guarantees but betting the cap hit in the first 3 years not more than $22mm per year if that. Bonus money out of that $110mm will be a split something like $50mm initial and then around bonus in 2 yr for say $20 million (this is how to spread the bonus over all six years instead of 5). And probably first 3 years of salary guaranteed, say $40mm, so really going into 2022, Dallas could walk away but with a $40mm cap hit.
Remember though, lots is going to change with the new CBA especially with the TV contracts going up and up, gambling money likely to even be more than the TV contracts, and other moneys. Also, betting Mahomes contract will easily exceed $40mm avg a year with his extension next year. Like it or not, it is the NFL we now live in.