Industry benchmarks for detailing both retail and wholesale work are easily obtained from Auto Laundry News and Professional Car Washing and Detailing magazine.
Benchmarks are available for a wide range of parameters including % of business by season and region, average time to complete, standard equipment used, distance travel by customers, number of competitors, line item operating expenses as % of gross sales, typical income, labor costs, % of business done by day of week, types and % of services offered, average price per service, typical traffic counts, etc.
I have this information dating back to 1991.
I would be glad to help if you are interested in making a lot of money detailing cars.