Your claim becomes worth more when you file a suit. The company will have to figure their lawyer time in valuing the claim. Talk to a buddy who is a lawyer. File a formal demand letter and ask for 100 cents on the dollar. It won't cost much to file a claim and you'll have the satisfaction of tooling around the insurance company. Worse case scenario is you get $750 and you are out of pocket your time and filing fees.
A year old bike simply does not depreciate as much as the insurance company is claiming.