Hi there,

I understood the objective slightly differently, which is average cost of the insurance premium. However, assuming we're talking about the cumulative cost of all damages from accidents, I would generally agree.

What you may want to consider though is whether there's a correlation between the price range of a car (indicative of a certain economic strata) and frequency of low, medium, and high impact accidents. If so, you might want to calculate the costs separately for the 3 groups of cars i.e. low, medium, high costs, and then add them up. This way, you can work with a matrix, which is tidier and easier to communicate than weighted averages.

Lastly, it may be worth pointing out that you do this for private passenger cars only and you're excluding everything that is 

1. Commercial cars such as taxis, rental cars, post delivery cars, etc.
2. Non-passenger cars e.g. trucks or other special vehicles that could technically also be termed “cars”

Hope this helps a bit. Best of luck!