GPT-5.6 Price Cut: Luna Falls 80%, Terra 20%
OpenAI cut GPT-5.6 Luna pricing 80% and Terra 20% on July 30, 2026, and added a Sol Fast mode. New pricing table and what changes for developers.
OpenAI cut GPT-5.6 Luna's API price by 80% and GPT-5.6 Terra's by 20% on July 30, 2026 — just three weeks after the GPT-5.6 family reached general availability. Luna now costs $0.20 / $1.20 per million input/output tokens (down from $1.00 / $6.00), Terra costs $2.00 / $12.00 (down from $2.50 / $15.00), and Sol's price is unchanged, but it gains a new Fast mode.
The new pricing, before and after
All prices are official list rates in US dollars per million tokens.
| Tier | Old input / output | New input / output | Change |
|---|---|---|---|
| GPT-5.6 Sol | $5.00 / $30.00 | $5.00 / $30.00 | Unchanged (new Fast mode added) |
| GPT-5.6 Terra | $2.50 / $15.00 | $2.00 / $12.00 | -20% |
| GPT-5.6 Luna | $1.00 / $6.00 | $0.20 / $1.20 | -80% |
Because both the input and output legs dropped by the same percentage on each tier, the blended cost of a typical request falls by exactly that tier's headline number regardless of your input-to-output token ratio. Cached input keeps its roughly 90% discount off the new base rate too: OpenAI's pricing page lists cached input at $0.02 per million for Luna and $0.20 per million for Terra as of this update.
Why OpenAI repriced a three-week-old model
OpenAI attributed the cut to serving-efficiency gains rather than a reaction to a specific competitor's pricing, saying the changes came from optimizations "across its AI training and inference stack, including software and GPU infrastructure," and that GPT-5.6 Sol itself helped optimize the production GPU kernels used to run the model family. That mirrors the release-week story for GPT-5.6 — OpenAI has said the model was tasked with improving its own token-generation efficiency — but this is the first time those gains have shown up as a public price cut rather than just a performance claim.
The repricing lands during the most price-competitive month the frontier-model market has had this year: Grok 4.5, Gemini 3.6 Flash and Muse Spark 1.1 all shipped within the same few weeks as GPT-5.6, each competing partly on cost per token. Cutting Luna's price to $0.20 per million input tokens puts it within range of Gemini 3.5 Flash-Lite's $0.30, undercutting the previous field of sub-$1 options rather than just matching it.
Sol gets a Fast mode instead of a price cut
Sol's per-token price did not move, but OpenAI added a Fast mode that runs API requests up to 2.5x faster than standard processing at double the price. It replaces the Priority Processing option OpenAI previously offered for latency-sensitive Sol traffic. For teams running interactive agent sessions where wall-clock latency — not token cost — is the bottleneck, Fast mode is now the lever to pull instead of trying to route around Sol with a cheaper tier.
What changes for developers
- Re-price existing evals before re-architecting. If you already route work across Sol, Terra and Luna by task difficulty, nothing about which tier wins on quality has changed — only the cost of getting it wrong by over-provisioning to a pricier tier.
- Luna is now cheap enough to be a default, not a fallback. At $0.20 per million input tokens, Luna undercuts Terra's old price by 92% and its new price by 90%. Workloads you previously kept on Terra "to be safe" — routing, tagging, short summarization — are worth re-testing on Luna now that the cost of being wrong about the tier choice is five times lower.
- Recheck cache economics. GPT-5.6 introduced a cache-write fee of 1.25x the uncached input rate at launch. That multiplier applies to a lower base price now, so the absolute cost of writing to cache fell alongside everything else — worth revisiting if you disabled caching for low-reuse prompts under the old numbers.
- Budget forecasts made before July 30 are stale. Any cost projection built on the GPT-5.6 launch pricing is now off by up to 80% on Luna-heavy workloads; rerun the math rather than applying a rough discount.
For a cross-vendor view with these updated numbers alongside Claude, Gemini, Grok and Kimi K3, see this site's AI model API pricing comparison.
The takeaway
A three-week repricing is fast even by 2026 frontier-model standards, and it signals that OpenAI expects cost, not just capability, to keep being a competitive axis for the rest of the GPT-5.6 generation. For developers, the practical move is the same one this site has recommended for every tiered model release this year: keep an eval suite that measures quality per tier, and let it — not the sticker price at launch — decide where a workload belongs, because that answer can change again before the next model does.
Frequently asked questions
How much did GPT-5.6 Luna and Terra prices drop?
On July 30, 2026, OpenAI cut GPT-5.6 Luna by 80%, from $1.00 / $6.00 to $0.20 / $1.20 per million input/output tokens, and GPT-5.6 Terra by 20%, from $2.50 / $15.00 to $2.00 / $12.00. GPT-5.6 Sol's pricing is unchanged at $5.00 / $30.00.
What is GPT-5.6 Sol's new Fast mode?
Fast mode is a new API option for Sol that runs up to 2.5x faster than standard processing at double the price. It replaces OpenAI's earlier Priority Processing tier for Sol.
Does the prompt-cache discount still apply after the price cut?
Yes. Cached input for both models keeps roughly a 90% discount off the new, lower base rate: $0.02 per million tokens for Luna and $0.20 per million for Terra, per OpenAI's published pricing.
Should I move workloads from Terra to Luna after this price cut?
Re-run your evals before deciding. Luna's input price is now 90% below Terra's, up from a 60% gap before the cut, which can justify routing more classification, extraction and summarization work down a tier — but only where your own quality tests hold at the cheaper tier.