The old trick back in the day was to increase premiums by an inconspicuous amount like $12. Over thousands of policyholders that could add up to a lot of free money. But I swear insurers aren't even trying these days. I think they realised everyone caught on so they just go all out in the hope that 1 person won't see their $400 enewal increase.
I just got a renewal letter which is $650 more expensive than last year, despite the facr that the driver is older and the car is worth even less.
A friend of mine got a $1200 increase one year. I think that's the record. Anyone ever seen higher?
EDIT - yes I drive a Mustang. Ho ha etc.