"We're paying for things that are running and doing nothing" is the most common cloud cost complaint, and also the least specific. Idle isn't one thing. An idle NAT gateway, an idle load balancer, and a 4%-CPU EC2 instance are three different problems with three different price tags and three different confidence levels about whether they're safe to touch. So here's the specific version: for each idle type, the threshold that makes "idle" a defensible claim rather than a hunch, and the mont...