Infracost is an open source cloud cost estimator in pull requests. When you change your infrastructure code (Terraform), we post a comment in the pull request, telling you the impact to your cloud bill, e.g. “this will increase your bill by 25% next month”.
I wish I had that when I was DevOps engineer and needed to reduce the costs of our cloud infra! But I definitely see the benefits now and from what I see, it's an awesome tool!