Insurance for salvage cars is no more expensive than insurance for regular title vehicles. It is often harder to find insurance for a salvage title vehicle. The majority of insurance companies will only issue liability insurance on a salvage title vehicle. Comprehensive and collision is usually out of the question with most insurance companies. In regards to the insurance rates for the liability coverage, they will not be much more than a normal car. The more important factors will be the vehicle type and your driving record. Keeping your driving record and credit score clean will result in the best rates.
For more info, see How to Buy Salvaged Vehicles from Insurance Companies