There is no possible use case in no possible universe where AWS is cost effective.
Renting the same compute resources wholesale will cost you 20 times less. (Not a typo.)
Right now, this is done on AWS, with lambda + S3, and costs under $0.02/month.
Can you point me to something more cost effective that that? Don't forget I also need backup for data, automatic failover in case of machine failure or crash, amd no maintenance (like OS upgrades) for 5+ years.
Enterprise workloads need compliance. AWS and GCP provide that. They are very few hosting companies out there who are better at security and compliance than those two.
You mean like S3 object storage? That costs less outside AWS because you are usually getting less. That's if you can get it at all.