I hate race cars. But I have 3 customers that I do graphics for. The first two are just basic designs with cut vinyl, very few sponsors. The other one is a sprint car. They have 2 cars and 3 wings. They don't care what the cost is. After the first year I learned to charge more for the design part because they make shirts and want to use all the sponsors from the car. I charge extra in the original invoice to cover my time and add a few minutes per logo for design. I take just the logos and send them in a single PDF.
There is a guy in the area that makes templates and does the design work but he doesn't print. I want to say he charges $600 for the design and that's for an A-Mod like the car below. The guy does really good work. The templates can be bought online anywhere so it's really the design part you need to make sure you are charging for. The racer pays around $3-3.50 per square foot for printing. I do not print it. I just know this becuase he has asked me to print it but I'm not able to beat that price so I pass. I do other work for the driver and sometimes he needs artwork for the design guy and sometimes I need artwork FROM the design guy. We make it work and all three of us get what we need.