The website at census.gov has statistics from the 2007 economic Census that will give you how many barber shops in your county, and average revenue.
Next, try a search on Google.com or another search engine for statistics on barber shops in the U.S. to get a list of additional resources. There are a lot of dead ends on that list, and some links to expensive market studies that you probably don't want, but there are also some good links to follow up.
It also might be good to get onto Google, Yahoo and Bing maps and search for barber shops locally, to see how many are in your immediate area. Then call them and ask about pricing. Look especially for one that might be more like yours, in a home, and spend a morning or an afternoon sitting somewhere comfortably where you can see people going in and out, to get a better idea about the volume of customers.