How is that even calculated? The GDP is the sum of all goods and services produced. I guess when Amazon sells an item the difference between the wholesale pric

How is that even calculated? The GDP is the sum of all goods and services produced. I guess when Amazon sells an item the difference between the wholesale price they pay and the end price they charge including shipping is a service, retail. But who has produced this service? The underpaid warehouse worker and delivery driver or Jeff Bezos? For income it's clear, for GDP I don't see it.