> think it's a bit unfair if you have to pay more for liability insurance because other people have chosen to buy more expensive cars
Yes, this. You can opt-out of insurance for your own vehicle if you want, but generally required to buy some minimum for everyone else's property that might be involved.
And this is reflected in your insurance premium. The cost to insure your own car is lower if you have a less expensive car.
I do, however, think it's a bit unfair if you have to pay more for liability insurance because other people have chosen to buy more expensive cars.