How much should I charge for a product cost 18$ (FBA)

Hi, I am using the Amazon calculator but still so confused because they shows the separate Amazon fulfillment fees. I thought I have already pay that monthly (the set up amount). 0.4 fees to sale clothes, Plus 0.4 storage, 0.2$ for barcode and cost to send it to Amazon. But the calculator show more than my own calculation. Can anyone help me? Thank you.I would appreciate if someone can help me to determine the amount I should charge customer TwT more over, how much profit should I expect for one product?