Beginner question

Hello everyone
I’m french and i’m thinking of selling on amazon products, and i tried the amazon calculator to see how much i could make, and I just don’t understand something : i’m planning on selling an object that’d cost me around 60 cents to sell it between 3 and 5 euros, so theoretically between 80% and 90% margin. I know amazon takes fees and ships the product, but i just don’t understand this calculator at all, like how can i lose money when selling something 5 bucks that costed me 60 cents