We can see this when researching the books as published to shareholders. When AWS was the "sole" player (first mover advantage) they had insane margins. Then competition stood up: GCP, Azure etc. And grew. Their margin has staid the same. And is roughly similar to that of GCP and Azure. Which means they either have secret gentlements agreement over pricing (highly illegal, not likely, the risk is just too high) or there's other mechanisms at play that allow them to keep dictating the price.
Cost of switching is very likely such a mechanism. They lure you "on board" then once you start feeling the pain of the high margins, there's simply no way you can move to a competitor with lower margins - either that competitor isn't one really (Digital Ocean, OVH, Linode) or these competitors aren't competing on your margin (GCP, Azure) and have similar margins.