The problem I have with this argument is that salaries don't have to be comparable to be competitive, because cost of living is different across the country. I make a fair amount less working in Ohio then if I moved to California, but I would also pay a lot more to live there.

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.