I am a vet student and although I personally don't have pet insurance I have a number of classmates that do. Unfortunately the companies that do cover rabbits or other exotics usually have a "call us for more information" or something similar rather than listing their prices online and I can't recommend a specific brand as being the best for rabbits. It is important to remember that all pet insurance works on a system where you pay upfront and then get reimbursed vs. the way human health insurance works. The veterinarians appreciate this because they still get paid and are able to set their own prices rather than having to haggle with the insurance companies.
I know VPI covers rabbits, but don't know their pricing, and I also know people who have had good experiences with VPI for their dogs or cats.
You should be able to see what they'll cover and how much they'll pay out for various diagnoses. Some plans will cover annual wellness things and others are essentially only for emergencies. In general it's better to get pet insurance when your pet is young to avoid things like preexisting conditions. For example, if you insure your rabbit right away and down the line you have tooth troubles, maybe they'll cover dentals, but if your rabbit has a history of malocclusion and then you get insurance, they're probably not going to cover extractions.
If you decide not to go with pet insurance, or even if you do, having an account set aside just for pet emergencies is definitely a good idea.