It’s a bit of an odd argument to make against a state sanctioned limit to labor that it should be driven by pure capitalism/free market principles.
So, making hiring these employees based on salary only means that places with a higher cost of living will be able to hire these employees for more typical rates, where-as companies in lower cost of living areas will have to pay well above average for the same employee. If actual salary wasn't a requirement, then midwest companies could still be competitive even while offering lower salaries.