I think that everyone who's used AWS or a competitor knows that it's very easy to rack up a large bill by accident. For companies, the main issue isn't the expense but the unpredictability.
If you're going for AWS, you should consider rewriting a lot of your services to use AWS features well.
Auto Scaling Groups and Fargate EC2 are some common components I see few companies using.
If your instances are the same size through the day, you are doing it wrong!*
*Exception: If you provide the same level of service and traffic 24/7.
Anecdata is terrible, but my experience running 1 Fargate container 24x7 on the lowest specs (0.25 CPU and 512 MB RAM) to handle baseline was was going to cost as much as a no-contract T3.micro EC2 instance with much more capacity (2 CPU and 1 GB RAM). AWS Kubernetes was also a bust at $120/mo just to get started (that's the cost before an EC2 server is provisioned).
EC2 is just EC2 with scaling groups while ECS is a fully non-managed solution that's for small items.