Passing the football was made the most important feature of offense by the League. They did so by the way they added and changed rules to protect Passers and Receivers.
So to not have a prolific Passer puts a team at a tremendous disadvantage.... which is why (once again) the Rams were so smart and pragmatic to go all-in to obtain Stafford.
The Teddy Bridgewaters are not going to lead teams to the Superbowl. They lead to records hovering around .500.
But, there's a limited number of these elite individuals that can do what the first tier or two of NFL QBs can do. Getting one is hard, and keeping one that you have is why it costs so much.