The loop is free, and that is not a trick
Amazon does not charge for agent orchestration. Its AgentCore pricing page meters Runtime, Gateway, Memory, Browser, Code Interpreter, Policy, Identity and Evaluations — there is no line item for the loop, because there is no charge for it. Microsoft says the same thing in a sentence: There is no additional charge for creating or running Foundry-native agents using prompts and workflows.
1 Any comparison page that prices the hyperscaler path as a stack of subscriptions is wrong, and we are not going to run one.
What you pay for instead is every call
The meter moves to the parts that do work. Retrieval is $1.00 per 1,000 Retrieve API calls2, or $4.00 per 1,000 Agentic Retrieve calls, plus $1.00 per 1,000 underlying Retrieve calls3 for the agentic variety. Guardrails are $0.104 for contextual grounding and $0.155 for content filters and denied topics. Gateway invocations are $0.005 per 1,000 Gateway API invocations6, runtime is $0.0895 per vCPU-hour7 plus $0.00945 per GB-hour8, and the index itself is $5.00 per GB of raw data, per month9.
Which comes out cheaper than us, and we would rather say so
Work those rates against a real workload and the platform fee lands well under our plan at both the volumes we publish. We could bury that. Instead: it is below, with the assumptions written out so you can change them. A comparison you can falsify in a spreadsheet is the only kind worth publishing, and a vendor that hides an unfavourable number has told you what its evidence trail is worth.
The argument that survives it
You can buy a score that grades an answer after the model has written it — that is what contextual grounding at $0.104 is, and the documentation is clear that the check runs on the output. You cannot buy retrieval that had no way to write it. Ours walks an index and opens the page it names; a path no listing offered is refused by the tool itself, before any text exists to be graded. The second thing you cannot assemble from a rate card is one version number over the library, the policy, the evaluation suite and the model, recorded with who published it and restorable. Seven metered services produce seven bills and seven change histories, and no sentence a compliance owner can sign.