And they won't win anything.... I think average QBs are paid because its one thing that owners, GMs, and coaches can all agree on. Owners love a marketable face for the franchise, while GMs and coaches love the short term job security and stability. Of course the security is all an illusion which evaporates after a couple years where no improvement is to be found.
Its a foolish path to follow and one I hope Flores and co manage to avoid.
For the sake of argument there are ~7 "elite" QBs. Brady, Brees, Mahomes, Rivers, Roethlisberger, Rodgers, and Wilson. Another ~4 that have had elite stretches and are young enough that they'll get at a minimum 2/3 yrs to show they can reach that status. Mayfield, Watson, Wentz, and Goff. You're right in saying that another 3 come into the league every year and even if they never show anything can be palatable starters with their rookie scale contracts for 3/4 years. So that leaves about 10 teams that should be looking for one of those next three every year.
To me its just a trend and one that will eventually die out. Its really hard for me to believe that there are only 10 people in the world that can play QB at a high level and gets even harder to believe every time I see a Foles or Keenum or Cousins come around and put together a great season. I'll acknowledge that it takes a rare confluence of events to produce one of these elites but its not solely based on the talent or mind the QB possesses.