I faced a similar issue at the company I work for (where a PM had activated an instance for months and racked up a $9k bill). I've been spending my coronavirus time hacking together a service that hopefully makes billing on AWS more clear. It does cost optimization and anomaly detection right now, and I plan on adding more features as I start to see more use cases.

Check it out if you'd like, and let me know what you think!

www.usage.ai