JackD-
I pay almost the same for my 500E as I do for my 300D or 300TE (all are within $100/yr). Reason is, a limited number of insurance companies remove the "HP", or High Performance, rating if the vehicle has 4 doors. So I pay a bit more simply because it's a more expensive car.
Learned this 2 years ago, shopped carriers and saved $1k/year