Amazon damaged stock and offering a refund that does not cover cost

I recently picked up a discrepancy in the stock levels at Amazon vs sales of the item. Amazon then referred me to a ledger report that indicated 3 items had been damaged (There was no proactive notification from Amazon) I was then refunded based on a internal calculation of my cost, minus the full Amazon FBA fee. I have disputed this twice and I keep getting asked for an invoice of my cost from my supplier.

My point is that the refund should be calculated on my selling price, not the cost price. Based on Amazons calculation, I will never recoup my cost, never mind realise a profit. How can this be right?