First of all, people sometimes use analogies that dont make sense to you. No need to be a dick about it. You could just make a better example.
Staying with cars, I see my mistake. Valve is not producing the cars in this example, valve is doing the car sales for the (small) manufacturer. They dont provide any part of the car, only the exposure and surrounding community. Its not nothing but has zero to do with the product.
What they are asking is „you can sell cars from our showroom, just dont sell them for cheaper than we do“. Which does make sense.