I have been saying this on this forum for months.
A long time ago, it was really hard to find someone smart enough, big enough and with a good enough arm to play QB at an NFL level. Positional scarcity was a huge problem. At lower levels, it was all option and T formations with teams just running the ball all the time. Some of the QB's starting in the 80's couldn't make a roster today.
Since that time, teams in lower levels have started throwing the ball . . . a lot. That has attracted people who could actually throw to learn the position in high school and go on to college. Even better, the race barrier is fully broken. A black guy who is athletic isn't automatically put at linebacker or WR. There are a lot of good QB's coming into the league on a regular basis.
There are a few elite QB's and a few sucky ones too. Outside of that, QB play is largely a product of coaching, line play, run game and receivers. If a QB gets a good play called and good protection, there are a LOT of people who can make the play nowadays.
IMO, unless you have one of those elite guys, you should just play moneyball. There is always another Tannehill out there you can pick up off the scrap heap. You can draft and develop QB's too. I would never, ever give a mid range QB 18% of the cap.
At some point a while ago, teams figured this out about the RB position. QB is next.