Bob, do you know how to do PDR or repair alloy wheels that have been curb rashed. If so, good for you, do it yourself. Most people who are paying to have their cars detailed would like to get their dings and wheels fixed while it's there. It adds to the total appearance of the vehicle. Most mobile PDR and wheel guys will give a discount to their commercial customers, and then the detailer is allowed to make some money off of the repair. I have some customers who bump my price 50%.
The cost of the detail remains the same. These are added services that he can provide through a sublet vendor that would make his business more profitable. I've been doing it for over twenty years now, but what do I know?