>>>Hi Nilesh sir
Hope you are doing fine.
>>>I have taken example of car holder who is best seller on Amazon and calculated its referral fees by using FBA calculator. For car holder, if you are going with FBA then referral fees is Rs.129.74 and FBA commision fees is Rs.71.60.
iGST for this product is 28%. You can calculate it by following link.
I have created a GIF file and you can calculate by yourself for your product.
Link to GIF : https://tinyurl.com/y8jdzebk
Let me know if you understand it.