Yup, we sure can get that $20 oil change, you must be talking about the oil change where the $7 am hour pot head, leaves the oil plug out.
I have family throught the country, that have service business and we discuss the area cost differences, they are there but there is a bigger difference in urban and metro areas, then different parts of the country, national firms that have service companes in every state, have little to no differences in their price structures.
Where some of the rural housing, that reguires longer travel. and has less services, and is taxed at a lower rate, the total cost of housing may be less, but, overall the same can be founf anywhere in the country.