"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 monthly dollar figure at us-east-1 list prices (early 2026, 730-hour month). Because "we have idle resources" starts a debate, and "these eleven resources burn $1,340 a month doing nothing" starts a cleanup.
The idle catalog, priced
The sub-5% EC2 instance. Threshold worth defending: average CPU below 5% AND negligible network traffic, sustained for 14 days. Both conditions matter; a proxy at 2% CPU pushing gigabits is not idle, and one quiet week proves nothing. The price is whatever the instance costs, in full: an m5.large burns about $70 a month to be 96% empty, an m5.2xlarge about $280, a c5.4xlarge about $500. Idleness doesn't discount the meter. The 14-day check:
aws cloudwatch get-metric-statistics --namespace AWS/EC2 \
