Devildog, yes, when you insure your cars, it is the cars you are insuring. However, there are a ton of options you are paying for. Besides all the coverages like what's included in the liability and full coverage portions, you are paying for the type of driving and the mileage a person will put on the vehicle. Whether it's a friend borrowing my car, or my son when he's home on vacation, they are considered low mileage use occurrences. They are included on your policy. Individuals in your household are considered heavy/heavier users; thus more miles; thus the increased chance of an accident. That is why they normally ask who will be the primary driver of which vehicle. They also price adjust for how many miles a year on average each car will have.
Now, each state (Regulated by the state board of insurance and legislation), determines the maximum amount of premium they are allowed to charge you. This is based on how many accidents occur per year in your zip code area, as well are the congestion and other attributes. That's why insurance prices aren't the same in all 50 states. As luigi mentioned, the insurance company is in business to make money. You can't blame them. And contrary to what some political pundits might say, the insurance company isn't always the bad guy. They are gambling that you won't have accidents. And hopefully you won't. But you might also live in an area where there's a lot of them by other people. You said you have 6 cars and 2 bikes. I'm not quite that many, but I have 5 cars and 1 bike. You are paying $675 PER MONTH. Well guess what, I DON'T PAY THAT MUCH IN THE ENTIRE 6 MONTH POLICY!!! Then again, I live in Wyoming. We don't have as many things to hit with a car out here. Thus, less claims. Thus, lower premiums for everyone. 1 full coverage, 4 liabilities, and a liability on the motorcycle for me, wife, son, and daughter is roughly $640 for 6 month policy.
Anyway, that's why while your car is what's insured, the cost goes up when you add "Full time" drivers to the policy; basically, the odds of more mileage on the vehicle(s), and thus greater odds of an accident. Mike...