When a specific pro athlete loses his place on a team, he is replaced by another pro athlete that will absorb the money.
While not being able to easily remove (or identify) bad teachers is a problem, the solution to that issue will not increase the pool of money available to pay the remaining good teachers (unless the solution involves removing but not replacing the bad teachers)
A teacher's salary is less "an average of the salary of their colleagues" as it is a division of the money allocated to education from taxes (and fundraisers).
While not being able to easily remove (or identify) bad teachers is a problem, the solution to that issue will not increase the pool of money available to pay the remaining good teachers (unless the solution involves removing but not replacing the bad teachers)
A teacher's salary is less "an average of the salary of their colleagues" as it is a division of the money allocated to education from taxes (and fundraisers).