GPT-5.6 Terra vs Claude Sonnet 5: API Cost Comparison (2026)
GPT-5.6 Terra or Claude Sonnet 5? Instead of comparing list prices, we compute the same workload on both (prices verified 2026-09-17). Spoiler: Claude Sonnet 5 wins on raw cost in fewer scenarios — but "when to pick each" matters more than the winner. Compare them live in the calculator.
| Rate per 1M tokens | GPT-5.6 Terra | Claude Sonnet 5 |
|---|---|---|
| Input | $2.00 | $2.00 |
| Cached input | $0.20 | $0.20 |
| Output | $12.00 | $10.00 |
Same workload, both models
| Monthly scenario | GPT-5.6 Terra | Claude Sonnet 5 | Difference |
|---|---|---|---|
| Support chatbot (150k requests, 400 in / 300 out tokens) | $660.00 | $570.00 | 14% in favor of Claude Sonnet 5 |
| Document workflow (22k runs, 3,000 in / 400 out tokens) | $237.60 | $220.00 | 7% in favor of Claude Sonnet 5 |
| High-volume classifier (1M requests, 300 in / 10 out tokens) | $720.00 | $700.00 | 3% in favor of Claude Sonnet 5 |
Your token shape decides: input-heavy workloads (documents, RAG) amplify the input-rate gap; output-heavy ones (content generation) weigh the output rate. Run your exact mix in the calculator with both preselected.
When to pick each
- Claude Sonnet 5 — when per-token cost rules: high volume, verifiable tasks, tight budgets. It comes out 14–14% cheaper in these scenarios.
- GPT-5.6 Terra — when the premium buys something you need (quality on your specific task, context, ecosystem). The only honest way to know: test your real case on both with a small sample.
- Both — the winning production pattern is often routing: easy requests to the cheap one, hard ones to the strong one.
Related guides: how AI API pricing works and how to reduce LLM costs.
Our read: both charge $2 per million uncached input tokens, while Sonnet's $10 output rate is lower than Terra's $12. On an output-heavy workload Sonnet therefore wins the published-price calculation; caching preserves the same relative gap.
The decision should turn on measured quality and operational fit. Run the same coding, structured-output and latency cases through both, then route by task if neither wins consistently.
Prices verified on 2026-09-17 against the provider's official pricing page. Estimates are for planning purposes only — always confirm current pricing with the provider.