no, self hosting is cheaper at scale. aws is good for prototyping and smaller scale apps. hybrid is kinda okay as well
This is true when the scale we are talking about is similar FB. otherwise self hosting won't be profitable. (We rarely develop applications that need to scales to that level.)
Even at that level, a lot of apps run on top of cloud providers.
PickMe runs on Azure
AirBnB runs on AWS
Instagram used to run on AWS (Until acquired by Meta)
Most of the netflix still runs on AWS. (I heard Netlfix is the largest external AWS customer)
the most popular service to run on own infrastructure is Cloudflare, I heard they are not even virtualizing, their OSs running on bare metal.
Also most of the banking and FinTech applications running on self hosted services due to regulations and security reasons.
Most of the companies go for self hosting due to other reasons like security, compliance, control etc, cost is not the only reason.