For property damages, you are entitled to be paid the fair market value of the vehicle right before it was damaged by the insurer's insured (and taxes and registration).
Fair market value is what you and the adjuster are negotiating now.
You need to find proofs that your vehicle was worth the amount you are claiming. Proofs may include receipts for modifications to the vehicle you recently did, pictures showing your vehicle was in above average condition, etc.
If you and the insurer cannot settle, you have the right to sue the person who did the damage. You should factor in the cost of suing in deciding whether to sue.
Without a personal injury claim, you likely will find that most attorneys would not take your case on a contingency basis.
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