GPT-5.6 Slashes API Prices Significantly: Terra by 80%, Luna by 20%

OpenAI has sharply cut GPT-5.6 API prices. Luna is down 80%, and Terra is down 20%.

Sol keeps its base price but now offers a faster Fast mode.

The ChatGPT app and Codex CLI auto-review feature have also been switched to GPT-5.6 Luna.

OpenAI says the lower pricing comes from model efficiency gains, making large-scale AI use cheaper.