It does not matter what the QB wants. It matters how the FO prepares for that day in advance.
Look how the Niners planned for Aiyuk. They new what he wanted, they new what they were willing to pay and then drafted a WR in round 1.
CD is holding all of the cards in Dallas. Aiyuk has no cards. Niners will offer what they think is fair and then trade him. That is how real GM's run an NFL team.
They will most likely talk to Purdy's agent early and if he is demanding $60M, they can draft another QB or pick up an experienced vet to be a Bus Driver.
But the 9er's arent obsessed with the model of creating a team around an (overpaid) Franchise QB.
As for the 'preparing for that day'......up to the morning of the GB game, EVERYTHING, was pretty much going to plan, (indeed there's a similarity with Mike Tyson, right upto the moment Douglas knocked him out.)
Im sure the PREPARED PLAN was for us to beat GB (AS EVERYONE EXPECTED), beat Detroit (as we had a couple of weeks previously) and then give 49ers a game in the Championship match up. THEN DAK GETS A CAREER ENDING, MARKET SETTING CONTRACT.
The first half of the GB game isnt conducive to paying that QB that money......especially as brings back up the previous two less than stellar play-off loses to the 9ers.
We can blame Jerry for not planning, however, Dak's GB performance is indelibly linked to the problem.