I don't think it is quite that Charles. My Cardinal (insured value $56,000) was $1100 per year on a 400 hour pilot. My 150/150 was $700 per year on insured value of $27500. The primary difference seemed to be in the value and even then it wasn't twice as much.
I think a standard 150 is more in the range of $500 to $600 from a discussion I recall several months ago. In any case, its something to look at. Double the seats and you double the liability exposure, double the hull value and you double the cost to total the aircraft in an accident. Insurance companies do look closely at this in addition to the safety record of the aircraft being insured. (which may explain why a Maule is so high)
Charles
