FBA vs FBM shipping

Okay, I looked up the product I am trying to sell, to ship it to the other side of the country it would cost me around 7$. I am trying to understand FBA and its benefits. I am trying to use the calculator but it does not let me put the shipping cost. Will I still have to pay ~7$ for shipping or does amazon pay for it? I’m sorry for such a stupid question, I am just trying to understand the benefits of FBA.