It's not like I don't believe that. But I am interested in any data taking salaries and qualification/experience into account. Local costs of living are certain

It's not like I don't believe that. But I am interested in any data taking salaries and qualification/experience into account. Local costs of living are certainly important for the employees, but not so much for the employer (assuming that they impact the salaries level to some degree). Even though the latter is probably still an approximation to the actual skills level of a developer.