OpenAI Releases GPT-6 Sol and Luna With API Prices Half Their Predecessors’

OpenAI has released GPT-6 Sol and GPT-6 Luna, two lower-cost models positioned as less-intensive alternatives to GPT-6 Astra. The company says both bring Astra-style training methods to faster, more affordable models for work at different scales.

Sol and Luna became available September 22 in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu customers. Luna is also available to Go and Free users in the ChatGPT desktop app. Neither model had reached basic Chat at publication.

The new price split

The clearest cost difference appears in the rate card. OpenAI lists Sol at $2 per million input tokens and $10 per million output tokens. Luna costs $0.10 for input and $0.50 for output at the same volume. OpenAI says both models cost 50% less than their corresponding GPT-5.6 versions.

OpenAI’s case rests on lower-cost accuracy

OpenAI’s pitch is not simply that Sol and Luna are cheaper. The company says the models make half as many factual errors as their predecessors. It also reports that Luna outperformed the GPT-5.6 release by 5.4% on AutomationBench while costing 58% less per task.

Those figures are OpenAI-reported benchmark and cost results, rather than a guarantee for a particular deployment. A lower rate can reduce spending, but a team’s outcome will still depend on the work it assigns and the model’s results in that setting.

What OpenAI says has changed

• Sol and Luna are positioned collectively as less-intensive alternatives to GPT-6 Astra.
• OpenAI says they use training methods similar to Astra’s.
• The company positions the pair for work at different scales.

A familiar pair in a new lineup

OpenAI previously described GPT-5.6 Sol as the flagship of its earlier series, with Luna as a fast, affordable model. The GPT-6 release places both below Astra instead, making them part of a broader set of choices organized around capability and cost.

Access is still uneven

The initial rollout favors paid Work and Codex customers. Free and Go users receive Luna only through the desktop app, while basic Chat had neither model at publication. That leaves access to the new pair dependent on product route and subscription tier.