Shipping Chargeback Deduction by Amazon

Hi,

I want to know regarding shipping chargeback that Amazon deducted from our account when the customer ordered below Rs.499/- product. PFB example.

If the product selling price is Rs.199/- and it is in FBA and customer have not prime account then Amazon charged Rs.40/- or Rs.50/- on the same. Now the total selling price is Rs.239/- or Rs.249/- but Amazon paying us only on Rs.199/-.

Amazon already charged all the charges like Referral Fee, Fixed Closing Fee, FBA Fees (Weight Handing & Pick and Pack) and GST on Fees. Then why they are deducting Rs.40/- as shipping chargeback.

When I contacted the seller support they saying that we are charging on the customer so that the owner on this amount is Amazon.

I want to know if a seller has a low ticket size products and FBA products seller are not able to charge any shipping cost to the customer. Then how can he justify the product cost? Because the Rs.40/- is fulfiller for his cost if he is selling low ticket size products.

Thanks