Summary
On July 30, 2026, OpenAI lowered GPT-5.6 API prices, cutting Luna by 80% (to $0.20/$1.20 per million input/output tokens) and Terra by 20% (to $2/$12), while flagship Sol held at $5/$30. OpenAI also launched a Fast mode for Sol in the API, delivering up to 2.5x faster responses at twice the price. The lower rates also apply to how Luna and Terra usage is metered inside ChatGPT Work and Codex.
What changed
GPT-5.6 Luna dropped from $1/$6 to $0.20/$1.20 per million input/output tokens (80% cut); Terra dropped from $2.50/$15 to $2/$12 (20% cut); Sol pricing unchanged at $5/$30. A new Sol Fast mode delivers up to 2.5x faster inference at 2x price. New rates also flow through to ChatGPT Work and Codex metering.
Why it matters
Aggressive cuts on the cheap and mid tiers push down the floor for high-volume agent and coding workloads, where token spend dominates cost. Holding Sol flat while discounting Luna and Terra signals OpenAI is defending margin at the frontier while competing hard on cost-sensitive, throughput-heavy use cases.
Evidence excerpt
OpenAI cut the price of GPT-5.6 Luna from $1 to $0.20 per million input tokens and from $6 to $1.20 per million output tokens; Terra drops from $2.50 to $2 on input and from $15 to $12 on output, while Sol stays at $5 and $30.