Luna, Terra and Sol. The cheapest tier costs $0.20 per million input tokens and $1.20 output, and OpenAI says it beats Fable 5 at roughly 99% lower cost per task. Terra matches GPT-5.5 quality at half the price and in 60% less time.
OpenAI introduced GPT-5.6 on July 30, 2026, organised into three tiers with astronomical names: Luna (economical), Terra (balanced) and Sol (frontier).
The prices, per million tokens: Luna costs $0.20 in and $1.20 out; Terra, $2 and $12; Sol keeps the previous generation's pricing.
The numbers OpenAI gives: Luna beats Fable 5 at roughly 99% lower cost per task, using 8.5× fewer output tokens while handling 2.2× more context. Terra reaches GPT-5.5 quality at half the cost and in 60% less time. Sol Fast runs up to 2.5× faster. Underneath, the company says it cut serving costs by 20% and improved token-generation efficiency by 15%.
Why it matters: for two years the argument against deploying AI agents at scale was the bill. An entry tier at $0.20 per million tokens changes that conversation entirely — and forces Anthropic and Google to answer on the same ground.
Go to OpenAI's original announcement →Source: OpenAI
Go to the original source →