Without the GTO, 80 more a month... with GTO, it was 240 more until they sent me the policy for this year, and it's 300+ more. No tickets or anything, just a young driver under the same roof. I had it on low mileage coverage, and even park coverage would only lessen it a bit. I don't know how they come up with this, but it's really crazy.
I could have changed the policy, but as soon as you change it you know something's going to happen. I changed my homeowner's policy from 500 deductible to 1000 after 14 years of nothing happening, and that year I had three claims.