# GPT-5.6 luna vs Llama 3.3 70B cost > These two cross at 0.95 on short prompts and at 0.19 on long ones, so the cheaper model flips on prompt length rather than on token ratio. URL: https://getculpa.com/gpt-5-6-luna-vs-llama-3-3-70b-versatile-cost Last reviewed: 2026-08-02 ## Answer GPT-5.6 luna undercuts Llama 3.3 70B on Groq for nearly every short-context workload and loses to it on nearly every long-context one. OpenAI charges a second, higher rate once a prompt gets long, which moves the crossover from 0.95 down to 0.19. Culpa, a local-first LLM cost, margin, and forecast ledger, meters which tier your calls landed in. ## Why this happens A crossover reads like a property of two models and it isn't. It's a property of two rate cards, and OpenAI publishes two of them for this model rather than one. Short prompts price at $0.20 per million input and $1.20 output. Long prompts price at $0.40 and $1.80. That second card moves the switch point from 0.95, where luna wins almost everything, to 0.19, where it wins almost nothing. Nothing about your traffic changed. The tier your prompts landed in did, and OpenAI's pricing table doesn't say where the boundary sits. ## What this usually looks like - Your spend on one model rose while your call count and your token counts held steady. - Prompt length grew after a retrieval change and nobody re-priced the model choice. - A comparison was run once, on short test prompts, and shipped against long production ones. - Nobody can say what share of your calls priced at the long-context rate. ## Common mistakes - Treating a published crossover as a fixed property of two models. Why it hurts: It's a property of the rate cards, and this model has two of them. Do instead: Compute the crossover per tier, then work out which tier your own traffic lands in. - Benchmarking a model choice on short test prompts. Why it hurts: The test prices on one card and production prices on another, so the result doesn't transfer. Do instead: Benchmark at your real prompt lengths, or price both tiers and plan against the worse one. - Assuming the long-context rate is a flat multiple of the short one. Why it hurts: Input doubles here while output rises by half, so one multiplier gets the crossover wrong. Do instead: Read both rows off the rate card. The two rates move by different factors. ## Self-check - Work out the distribution of your prompt lengths rather than the average. - Establish what share of your calls priced at the long-context rate. - Compute output divided by input, then compare it against 0.95 or 0.19 depending on the tier. - Price a month at both tiers and treat the gap as your exposure to prompt growth. - Re-check after any retrieval or context change, because those move prompt length directly. ## One workload, two rate cards, opposite winners (illustrative) Llama 3.3 70B Versatile on Groq at real rates of $0.59 per million input and $0.79 output, against GPT-5.6 luna at $0.20 and $1.20 short-context and $0.40 and $1.80 long-context. The Groq and short-context luna rates are in Culpa's price book, effective 2026-07-02 and re-verified 2026-08-02. The long-context rates were read off OpenAI's pricing page on 2026-08-02 and aren't in the book yet. Volumes are modelled. Short-context crossover: ($0.59 - $0.20) / ($1.20 - $0.79) = 0.95 Long-context crossover: ($0.59 - $0.40) / ($1.80 - $0.79) = 0.19 One workload, 100M input and 40M output, a ratio of 0.40 Llama 3.3 70B: (100 x $0.59) + (40 x $0.79) = $59.00 + $31.60 = $90.60 GPT-5.6 luna short-context: (100 x $0.20) + (40 x $1.20) = $20.00 + $48.00 = $68.00 GPT-5.6 luna long-context: (100 x $0.40) + (40 x $1.80) = $40.00 + $72.00 = $112.00 Same tokens and the same ratio, and luna moves from cheapest to dearest At a ratio of 0.40 luna costs $68.00 on short prompts and $112.00 on long ones, so the same traffic swings from 25% below Llama 3.3 70B to 24% above it. Prompt length decided this, not the token ratio everyone compares. ## Cost figures Every figure carries its confidence and its source. No figure on this site is provider-reported. - 0.95 — output-to-input ratio at which these two cost the same on short-context prompts [calculated] Source: ($0.59 - $0.20) divided by ($1.20 - $0.79), using real Groq Llama 3.3 70B Versatile and OpenAI GPT-5.6 luna short-context rates per million from the price book, effective 2026-07-02 and re-verified 2026-08-02. - 0.19 — the same crossover once a prompt prices at OpenAI's long-context rate [calculated] Source: ($0.59 - $0.40) divided by ($1.80 - $0.79), using the long-context rates read off OpenAI's pricing page 2026-08-02. Those rates aren't in Culpa's price book yet. - $68.00 to $112.00 — modelled monthly cost of one workload across both context tiers and both models [estimated] Source: The totals in the teardown arithmetic at real rates. A range because the token volumes are modelled. ## FAQ Q: Is GPT-5.6 luna cheaper than Llama 3.3 70B? A: On short prompts, almost always. The two cross at an output-to-input ratio of 0.95 there, which little real traffic reaches. On long prompts they cross at 0.19, so luna only wins on unusually input-heavy work and Llama 3.3 70B takes the rest. Q: Where does the long-context rate start? A: OpenAI's pricing table publishes short-context and long-context columns without stating the token boundary in the table itself, checked 2026-08-02. Until it's published, the practical answer is to measure what share of your own calls priced at the higher rate. Q: Does this apply to the other GPT-5.6 models? A: The two-tier structure does. Terra carries the same short and long columns, while GPT-5.4 mini shows a dash in the long-context columns instead. So the tier question belongs to the 5.6 family rather than to OpenAI's catalogue as a whole. ## Sources - OpenAI API pricing: https://developers.openai.com/api/docs/pricing - Groq pricing: https://groq.com/pricing Run the free Cost Leak Scan: https://app.getculpa.com/scan?source=pseo&slug=gpt-5-6-luna-vs-llama-3-3-70b-versatile-cost&cluster=model_compare Machine-readable index of every guide: https://getculpa.com/api/pages Human-readable index of every guide: https://getculpa.com/guides Site overview: https://app.getculpa.com/llms.txt Privacy: Culpa runs on your infrastructure. Your prompts and responses never leave it. Culpa counts calls to run your plan, and it fails open, so if it ever breaks your app keeps running.