Is that not only a matter of the # of vehicles, but also the age of the driver(s)?

I seem to recall you have a few teenagers in the house? That might be the difference. Young driver insurance can be 5x the cost (or more) of drivers who are older than 25. Frankly I’m not sure how young adults can afford to drive.
In any case, I hope you find a more affordable insurance option! I wonder if there are groups you’re affiliated with already, who would offer cheaper insurance. Church groups, AARP, sometimes credit unions, AAA, professional associations, stuff like that. If you’re a member of any such groups, you might want to check with them to see if they offer anything along those lines. Just tossing out some ideas..