The crux of this problem isn't what they pay Prescott, it's what they're paying the OL, Lawrence and Elliott and may have to pay Cooper. That's where the impact of paying a QB 35-40M a year comes into play.
What are the other teams that have the 30m+ QB's paying their other players? GB, NO and SEA?
The key to this is if you have a Tier 1 QB, you can get by with letting other players walk as long as you keep him upright and with weapons. But paying a Tier 2 QB Tier 1 money as well as that OL, DE, RB and maybe WR Tier 1 money and now that team has a major challenge with the rest of the team and this team is going to see that in having to let their best DB, by far, walk.