The cost increases are frustrating as well as expensive but they had to change their pricing models a year or two ago as a result of some legal challenge around differential pricing?
Let’s not forget they are also responding to increase in the general price of cars, costs for repairs, more expensive labour costs and such. Ultimately, they are a business and need to provide a return for their shareholders/investors.
Cheap insurance is not always good insurance either.
None of that describes a cartel, oligopoly or otherwise does it?