The more cars you have the cheaper it gets.
I have six vehicles insured and 2 teenage boys driving, and it costs me right at $3000 per year. I only have full coverage on the MB and a Lexus. But the 97 Yukon with no collision is the most expensive to insure. $650 for the year. I guess the heavier the vehicle is the more it costs. I have Nationwide with the house on it as well.