If Dak and Dallas don't agree to an extension, both sides lose.
Dak may get his massive contract elsewhere but it is a huge gamble that he will end up on a winning team and we all know how coaches and offensive schemes can either help or hurt QBs. If Dak trends downward, he more than likely doesn't cash in on a 2nd massive contract 4 or 5 years from now. Let's face it, Dak is a good QB but I think even the supporters (myself included) know that it is possible he could take a step back if Cooper or Smith go down. Not to mention, Dallas is a spotlight team and being successful in Dallas can produce huge endorsement deals.
Dallas won't have to commit and pay long term money to a QB but it will also mean they will have to fill a major void in the next season or two.
Both sides have to give a little to get this deal done and if no agreement is made, then everyone loses.