You're missing the point. Everyone expects an "elite" QB, but don't understand the definition or that it's rare.
Unless you have an alternative to Prescott?
I don't need an alternative to Dak right now. He's under contract for 2019. I can tag him for at least two more years before his tag number becomes really excessive.
I can let him play in 2019 and approach him with a contract if he plays well for half the season or wait until after the season. If he balks, I can tag him and try to work out a deal in 2020. If he shows in 2019 he's more the bus driver than the put the team on your back type QB, then I've saved myself a lot of cap headaches and I can start looking for another long term option.
The flip side to this.............. I go out and sign Dak now and hand him a contract that has a $35MM AAV (or whatever over $32MM contract people want to hand him)........ and he plays like an average QB. I am now staring at the possibility that I am eating up massive cap space for 3-4 years on a QB that isn't really all that good.
Sure, if you sign him for $32MM and he plays well you may have a "bargain" and you might have to pay him $37MM next year if you don't sign him now. But to me, that's just the smart play and paying the premium is worth insuring myself against the downside.