GPT-6.1 Terra vs GPT-6 Luna
GPT-6 Luna is 10.0x cheaper than GPT-6.1 Terra on our example workload, at list prices.
Side by side
| GPT-6.1 Terra | GPT-6 Luna | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Input / 1M tokens | $1.00 | $0.100 |
| Output / 1M tokens | $5.00 | $0.500 |
| Output price ÷ input price | 5.0x | 5.0x |
| Blended / 1M (3:1) | $2.00 | $0.200 |
| Context window | 1.05M | 1.05M |
| ≈ English words that fit | 788,000 | 788,000 |
| 1,000 calls (2000+500 tok) | $4.50 | $0.450 |
| AA Intelligence Index | 51 | 28 |
| LMArena Text | n/a | 1441 |
| Blended $ per AA index point | $0.039 | $0.007 |
List prices from official pages (OpenAI, OpenAI), verified 2026-11-04. Benchmarks from public leaderboards (Artificial Analysis, LMArena), not run by us. Word counts use the rough 0.75 words per token rule for English. "$ per index point" is our own arithmetic (blended price ÷ index score), a rough value-for-money signal, not a benchmark.
What real workloads cost
Four example request shapes, priced at list rates with no caching or batch discounts. Monthly figures assume 100,000 requests.
| Workload | GPT-6.1 Terra | GPT-6 Luna | Gap |
|---|---|---|---|
| Support chat reply a short system prompt, recent chat history and a reply | $0.00450 each $450.00 / mo | $0.00045 each $45.00 / mo | 10.0x |
| RAG answer a question plus about 20K tokens of retrieved documents, and a cited answer | $0.0240 each $2,400.00 / mo | $0.00240 each $240.00 / mo | 10.0x |
| 10-step agent task an agent loop of 10 model calls, each re-reading about 8K tokens of context and emitting a 400-token tool call | $0.1000 each $10,000.00 / mo | $0.0100 each $1,000.00 / mo | 10.0x |
| Long-report summary one 200K-token document summarized into about 2K tokens | $0.2100 each $21,000.00 / mo | $0.0210 each $2,100.00 / mo | 10.0x |
When to pick each
- Pick GPT-6 Luna when cost is the main constraint: at list prices it is 10.0x cheaper than GPT-6.1 Terra on a typical 2,000-in / 500-out call ($0.4500 vs $4.50 per 1,000 calls).
- Pick GPT-6.1 Terra when answer quality matters more than price: it scores 51 vs 28 on the Artificial Analysis Intelligence Index, and costs 10.0x more per call.
- Both come from OpenAI, so switching between them is usually a one-line model-name change on the same API and SDK; many teams route easy calls to the cheaper one and hard calls to the other.
Context and pricing limits
- GPT-6.1 Terra: 1.05M tokens of context. GPT-6 Luna: 1.05M. Same size.
- GPT-6.1 Terra: Short-context (<=272K input) price. The prices above are this tier; check the official pricing page before committing.
- GPT-6 Luna: Short-context (<=272K input) price. The prices above are this tier; check the official pricing page before committing.
- Cached input, batch and off-peak discounts can cut real bills a lot and differ by provider; they are not included here.
FAQ
Is GPT-6 Luna cheaper than GPT-6.1 Terra?
Yes, on our 2000-in / 500-out example call it costs $0.00045 vs $0.00450, 10.0x less.
Which has the larger context window?
Neither: both accept 1.05M tokens.
Which scores higher on benchmarks?
GPT-6.1 Terra scores 51 vs 28 on the Artificial Analysis Intelligence Index. LMArena Text: GPT-6.1 Terra n/a, GPT-6 Luna 1441. Benchmarks are averages; test both on your own prompts.
Run your own numbers in the token cost estimator · GPT-6.1 Terra pricing · GPT-6 Luna pricing · All comparisons