High rental values ($4k+) in non coastal cities

I get that there are an abundance of people willing to pay high rent ($4,000 or more per unit) in places like NY, SF, LA, Miami etc. But what about midwestern cities like Chicago, Dallas, Houston and Phoenix/Tempe etc.? If the economy has some slight shocks, are those places going to be filled out a couple years down the road with all the cheaper options available in these places? 

Any general opinions on high rental properties? The ROI compared to multiple lower rent properties as far as 10, 15, 20 year periods?