Ex-insurance company sales manager here. I agree that the insurance premiums are a good indicator but they will stay higher than normal vehicles because of the way insurance works. Reinsurers buy the potential risks in bulk and the way it is priced is putting similar risks and assets in a basket and then comparing the data they have about event possibility of the risk. The big data usually gives a pretty good indicator of the total number of accidents, incidents that will happen.

I have been away from the insurance sector for a couple years now, but before the electric car market was evaluated as its own class. This creates a huge problem because you can't distribute the claims optimally. If I simplify it you get (electric car insurance claims/electric cars that have insurance) + operation costs + profit %. Whereas in normal cars, your premium is decided based on the drivers age, previous accidents, car's age, car's color, the horse power, where the person lives, how much they drive etc. In the company I worked for we optimized the premium with over 200 data points.

You can't use the same optimization regarding electric cars because the market is so small and the data isn't there yet. Moreover insurers increase premiums to be on the safe side.