Claude Opus 5.5 vs GPT-6 Astra
Claude Opus 5.5 costs $4.00 / $20.00 and GPT-6 Astra costs $10.00 / $50.00 per million input / output tokens. At a typical 3:1 mix, Claude Opus 5.5 is 2.5× cheaper than GPT-6 Astra. On Epoch AI’s Capabilities Index they score level (169 vs 169, within each other’s margin of error).
Price
Claude Opus 5.5 is 2.5× cheaper per token
On a coding agent: $853 vs $2,598 a month (3× less)
Capability
Level
Claude Opus 5.5 169 (166–172)
GPT-6 Astra 169 (166–173)
GPT-6 Astra 169 (166–173)
Best value at Claude Opus 5.5’s level
GPT-6.1 Terra, 4× less
Level with or above Claude Opus 5.5 · $213 a month on a coding agent · Every option
Input
$4.00
per 1M
Output
$20.00
per 1M
Cached
$0.20
1M context
Input
$10.00
per 1M
Output
$50.00
per 1M
Cached
$1.00
1.05M context
Side by side
✓ marks the cheaper price, larger context window, bigger discount or higher score.
| Detail | Claude Opus 5.5 | GPT-6 Astra |
|---|---|---|
| Price per 1M tokens | ||
| Input | $4.00Lowest | $10.00 |
| Output | $20.00Lowest | $50.00 |
| Blended (3 in : 1 out) | $8.00Lowest | $20.00 |
| Cached input | $0.20Lowest | $1.00 |
| Batch or off-peak discount | 50% (batch) | 50% (batch) |
| Long prompts | Same rate at any length | Over 272K: 2× in, 1.5× out |
| Limits and model | ||
| Context window | 1M | 1.05MLargest |
| Capability score Epoch AI index | 169 | 169 |
| Arena text score 25 Sep 2026 | 1509Highest | 1478 |
| Released | 22 Sep 2026 | 3 Sep 2026 |
| Open weights | No | No |
| Status | Current | Current |
| Checked | ||
| Price checked | 11 Nov 2026 Anthropic pricing | 2 Nov 2026 OpenAI pricing |
Monthly cost on three workloads
List prices, no batch discount. The cached share applies where a model has a cache rate.
| Workload | Claude Opus 5.5 | GPT-6 Astra | Difference |
|---|---|---|---|
| Customer chat assistant50,000 conversations a month, about 2,000 tokens in and 400 out each; 50% cachedPrice this workload in the calculator | $610Lower | $1,550 | $940 |
| Document Q&A (RAG)20,000 questions a month over retrieved documents, 12,000 in and 600 out; 30% cachedPrice this workload in the calculator | $926Lower | $2,352 | $1,426 |
| Coding agent400 tasks a month, 40 steps each with a growing context; 85% cachedPrice this workload in the calculator | $738Lower | $2,163 | $1,425 |
How they differ
- Claude Opus 5.5 is cheaper on input ($4 vs $10).
- Claude Opus 5.5 is cheaper on output ($20 vs $50), which matters most for long answers and reasoning models.
- GPT-6 Astra accepts longer prompts (1.05M vs 1M tokens).
- Cached input is cheaper on Claude Opus 5.5 ($0.20 vs $1), which favours agents and chat apps that resend the same context.
- Both score 169 on Epoch AI’s Capabilities Index, so on general benchmarks they’re level. Claude Opus 5.5 is 2.5× cheaper for a similar score.
- On the Arena text leaderboard (25 Sep 2026), Claude Opus 5.5 scores higher (1509 vs 1478). Test both on your own prompts before deciding.
Recent changes
All changes- OpenAI launched GPT-6.1 Terra at $1 / $5 per 1M tokens, with cached input at $0.05: half the price of GPT-6.1 Sol.
- GPT-6.1 Sol replaced GPT-6 Sol at the same $2 / $10 per 1M tokens, with cached input cut from $0.20 to $0.10.
- ▼ 20%Claude Opus 5.5 launched at $4 / $20 per 1M tokens, 20% below Opus 5.
$5 / $25→ $4 / $20 - OpenAI launched GPT-6 Sol at $2 / $10 and GPT-6 Luna at $0.10 / $0.50.
- OpenAI launched GPT-6 Astra at $10 / $50, its most expensive standard model.
Related comparisons
Compare up to four
Gemini 4 Argon vs GPT-6 Astra$2.00 / $10.00 · $10.00 / $50.00- Gemini 4 Argon vs Claude Opus 5.5$2.00 / $10.00 · $4.00 / $20.00
- Claude Opus 5.5 vs GPT-6.1 Sol$4.00 / $20.00 · $2.00 / $10.00
- Claude Fable 5.2 vs GPT-6 Astra$8.00 / $40.00 · $10.00 / $50.00
- Claude Fable 5.2 vs Claude Opus 5.5$8.00 / $40.00 · $4.00 / $20.00
Kimi K3 vs Claude Opus 5.5$3.00 / $15.00 · $4.00 / $20.00- Gemini 3.1 Pro vs GPT-6 Astra$2.00 / $12.00 · $10.00 / $50.00
- Claude Opus 5.5 vs Gemini 3.1 Pro$4.00 / $20.00 · $2.00 / $12.00
Grok 4.7 vs Claude Opus 5.5$2.00 / $6.00 · $4.00 / $20.00