That may be, but the CFIs at 99% of the flight schools are not on salary. They are paid for the time charged the student, just like the Part 61 CFI you hired.
The school provides insurance, workers comp, and pays the employers % payroll taxes by charging the student more than the CFI hourly wage.
There are very few flight schools outside the university setting that can pay 10 CFIs to sit around when weather is below training minimums, it is too windy or there is connective activity. You don’t work, you don’t get paid.