I can rephrase that there is some point X where X is the amount you pay employees, such that you don't make any money on T time scale. You can't say that you always get better productivity as you pay more and more. There comes a point where paying them more does not improve their efficiency or your business enough to justify the higher salaries being paid out.

I'm not saying that paying min 70k is beyond this point where paying them won't help you on T time scale, but it needs to be evaluated. You can't just assume that paying someone more will be more than made up for in increased long term efficiency.