They're cheap and reliable, that generally comes at the risk of early termination. I don't think you can have a cheap, reliable, unlimited service; pick two at most.
If everything is metered it seems kind of odd to complain about a lot of activity. Since it's literally the thing you make money with.
Minor nitpick, but this is categorically not true. As a customer, one who proactively worked with AWS AMs, SAs, and S3 engineers directly before making the change, I still took down S3 by just changing how new files were stored in our S3 bucket. Yes, this S3 bucket was at the time the largest bucket (based on number of files), but still not “simply unbreakable”.