Claude Opus 5.5 vs GPT-6.1 Terra
GPT-6.1 Terra is 4.0x cheaper than Claude Opus 5.5 on our example workload, at list prices.
Side by side
| Claude Opus 5.5 | GPT-6.1 Terra | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input / 1M tokens | $4.00 | $1.00 |
| Output / 1M tokens | $20.00 | $5.00 |
| Output price ÷ input price | 5.0x | 5.0x |
| Blended / 1M (3:1) | $8.00 | $2.00 |
| Context window | 1M | 1.05M |
| ≈ English words that fit | 750,000 | 788,000 |
| 1,000 calls (2000+500 tok) | $18.00 | $4.50 |
| AA Intelligence Index | 59 | 51 |
| LMArena Text | 1509 | n/a |
| Blended $ per AA index point | $0.136 | $0.039 |
List prices from official pages (Anthropic, OpenAI), verified 2026-11-04. Benchmarks from public leaderboards (Artificial Analysis, LMArena), not run by us. Word counts use the rough 0.75 words per token rule for English. "$ 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 | Claude Opus 5.5 | GPT-6.1 Terra | Gap |
|---|---|---|---|
| Support chat reply a short system prompt, recent chat history and a reply | $0.0180 each $1,800.00 / mo | $0.00450 each $450.00 / mo | 4.0x |
| RAG answer a question plus about 20K tokens of retrieved documents, and a cited answer | $0.0960 each $9,600.00 / mo | $0.0240 each $2,400.00 / mo | 4.0x |
| 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 | $0.4000 each $40,000.00 / mo | $0.1000 each $10,000.00 / mo | 4.0x |
| Long-report summary one 200K-token document summarized into about 2K tokens | $0.8400 each $84,000.00 / mo | $0.2100 each $21,000.00 / mo | 4.0x |
When to pick each
- Pick GPT-6.1 Terra when cost is the main constraint: at list prices it is 4.0x cheaper than Claude Opus 5.5 on a typical 2,000-in / 500-out call ($4.50 vs $18.00 per 1,000 calls).
- Pick Claude Opus 5.5 when answer quality matters more than price: it scores 59 vs 51 on the Artificial Analysis Intelligence Index, and costs 4.0x more per call.
- Pick GPT-6.1 Terra if a single prompt can exceed 1M tokens (about 750,000 English words): its window is 1.05M.
- They come from different providers (Anthropic and OpenAI), so switching means a second API key, SDK and billing account, and tool-calling formats differ. Our schema converter outputs both formats from one JSON Schema.
Context and pricing limits
- Claude Opus 5.5: 1M tokens of context. GPT-6.1 Terra: 1.05M. GPT-6.1 Terra holds 1.1x more.
- GPT-6.1 Terra: 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-6.1 Terra cheaper than Claude Opus 5.5?
Yes, on our 2000-in / 500-out example call it costs $0.00450 vs $0.0180, 4.0x less.
Which has the larger context window?
GPT-6.1 Terra, with 1.05M tokens vs 1M.
Which scores higher on benchmarks?
Claude Opus 5.5 scores 59 vs 51 on the Artificial Analysis Intelligence Index. LMArena Text: Claude Opus 5.5 1509, GPT-6.1 Terra n/a. Benchmarks are averages; test both on your own prompts.
Run your own numbers in the token cost estimator · Claude Opus 5.5 pricing · GPT-6.1 Terra pricing · All comparisons