What do buyers pay for shipping using Amazon MCF on Shopify site?

I’m talking to Amazon customer service and they are not able to tell me. I want to know what customers going to my website (Shopify site with Amazon MCF installed) are paying for shipping. I haven’t had any orders yet but if I don’t know what they’re charging, I won’t know if it’s reasonable. The customer service guy is just saying it’s by weight, location etc.. but is there any way to find out what it is?