It is likley the number of cars, if they see that you own multiple cars they know you can not possibly be driving them all at once.
I pay right at $500 every six months on my 2000 base (full coverage) and a 96 nissan hardbody pickup (liability only). I have a perfect driving record and no tickets ever and am 33. I have Geico insurance. I do carry the higher $300k limits but I think my deductible is $1500 too.
Shoot, I pay around $270 every six months with $300k liability and $0 deductible full coverage on the Box - and that is with one at-fault accident (hit a Merc S500 with the Soul last summer ) I LOVE North Carolina insurance rates!!
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Current: 2000 Boxster S....2018 Clubman JCW
Previous: '71 914 2.2 - TX license plate: "E-GO"....'73 914 1.7....'74 914 1.8....'73 914 2.0 - Saturn yellow with all original 2.0 options- R.I.P..... '74 914 1.8 with 916 body kit.... '72 914 1.7 - my very first car
Also: '09 Cooper Clubman....'90 Miata.... '80 MGB.... '76 TR-7
My Boxster is on my insurance policy as a "pleasure" vehicle, driven less than 6500 per year. 12 months full coverage on my policy that has two other cars and my homeowners is $297.00 .
I just moved back home to FL after being in NC since 96, major sticker shock on car insurance down here. Crazy...
I am in NC and hear that all of the time - that we have great car insurance rates. I don't understand why the insurance companies are trying to get rid of the insurance rate regulation so they can offer us lower rates.