The insurance company is only obligated to go by book value in most states. While most of the major carries have full replacement for cars under 1 year now, guessing they went with the bargain price carrier. However, you can go after the company and the individual for negligence in the amount of the difference to pay for replacement, as well as inconvience/distress and lawyer fees. Any reasonable judge would likely take your side.
Good luck and be persistent! Get lots of documentation, such as print off price sheets and auto ads with today's date for your exact make/model. The downside to expensive cars is they can depreciate pretty fast, but Corvette's have a large following and it's a breeze to find the going market value.