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.
This is [unfortunately] correct. If you marry your company's destiny to AWS, their managed products are far more cost-effective than using them as a datacenter [no doubt this is intentional by Amazon]. If you're just using the EC2 services, much like owning the hardware, unused CPU and RAM is wasted money.
I recently gave Fargate a try and was very unimpressed with the costs.
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).
The ECS one is weirdly difficult to set up. If you just want Docker Repo (ECR) -> deploy with some config -> expose a single ingress point it sounds perfect, but I had a TON of trouble with it recently
