Flying Business class award ticket purchased using US miles

Unfortunately TK lost my single checked bag and after several months finally admitted that suitcase is indeed lost

Baggage Irregularity Report filed immediately upon arrival into IST and finally received correspondence asking me full details of suitcase contents with descriptions and values.

An offer as compensation from TK is seriously below purchase or replacement values. Many of these items were purchased weeks before travel

I have not been asked for receipts or replacement values. I want to decline the TK offer as insufficient compensation. How are my chances of getting a more substantial offer of I choose to decline the initial offer

Thanks for any guidance.
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