There are only a handful of companies in the world that AWS would be more expensive than having your own cloud. Just the baseline costs of having 24/7 availability requires minimum 5 full time engineers (3 shifts + cover for sick / vacation). So that's $1 million a year right there, and we're already well over the cloud spend of the vast majority of companies. If you want multi region that's now $2 million. And we're still just covering the cost of the people who have to be on call to deal with hardware issues. Now how much is it going to cost to develop the software tooling required to manage the whole thing from your office?
I agree with the basic premise and math here but getting to true 24/7 uptime in the cloud will require a minimum of 2 full time cloud engineers or infra people. If you're spending another 500K in usage costs you're almost at a million. For most, the cloud is the right option because maintaining servers is a pain and modern clouds offer a lot of additional features that may be useful, but it doesn't mean it's a massive win for the bottom line. There are lots of small and large companies that could run servers on prem or in their own datacenter and it would make financial sense, but they'd have to attract the talent to build and operate, which is harder than just paying enough.
This is apples and oranges, though. AWS does not manage your whole product. Are you going to have 24/7 on call for the parts that you manage? If not, why do you need it for the parts AWS manages? The reality is that most smaller companies do not need this level (and frankly I think most people significantly overestimate the overhead of running your own box. A heck of a lot of cloud deployments could be two servers in a co-location with one of them being a warm spare, and have equivalent service levels for their product in practice).
Eh this is true but in practice "my RAM stick went bad" is 0% of our downtime. It's almost always that we screwed up something in the app layer. And my company of ~100 does have 5 engineers on call 24/7. It's baked into our salary to do that.