I recall reading multiple AskHN posts about people trying to get attention from a cloud provider because they ran up thousands of dollars in charges accidentally. I've seen large companies do this too, even if you think something is just a dev environment, its the cloud provider's production environment and they will charge you per their ToS for everything you use, doesn't matter what the customer usage profile looks like.

Experienced dev with limited hands-on big tech infrastructure experience. Based on the results I get from LLMs in domains I understand how get they even get this stuff running using AI?

I can accept this is true, they will for sure exist. Of course if this they ability to make choices, technical or not, they are completely doomed.