Not particularly interested in this discussion or political topics in general (really don't have an opinion either way), but I did want to address a point you're trying to make.
These salaries seem to accurately reflect the average range of people in the Des Moines tax field. Adjusting those salaries for cost of living in other cities, gives us what we should expect if they were effectively paid the same.
You say salaries in Chicago are only about $10,000 higher, but if they aren't at least $16-24k higher to account for cost of living, you're simply being paid worse than in Des Moines.
Likewise, in Minneapolis, you quoted a $6-8k difference. You only just break even using the low end of average salaries and the high end of your estimate. Anything else is a loss and you'll be paid less for the same work, which is to say nothing of the fact that differences in population make it distinctly not the same work load.
So, yes, "cost of living accounts for a lot of that." In this particular occupation, you make significantly more money (doing less and likely easier work) in Des Moines. I suspect that holds true for a lot jobs, although probably not all.