Cheaper overall
Claude Sonnet 5.5
80% lower blended rate
Higher benchmark scores
Claude Sonnet 5.5
leads on 5 of 8 figures
Bigger context window
GPT-6 Astra
1,050,000 vs 1,000,000 tokens
Cheaper cached input
Claude Sonnet 5.5
$0.10 vs $1.00, 90% less
Where each one wins
Claude Sonnet 5.5
- Cheaper input tokens $2.00 vs $10.00, 80% less
- Cheaper output tokens $10.00 vs $50.00, 80% less
- Cheaper cached input $0.10 vs $1.00, 90% less
- Cheaper on all four workloads
- Higher overall intelligence (Intelligence Index) 56 vs 52.7
- Higher expert-exam performance (Humanity's Last Exam) 55 vs 54.7
- Higher long-context reasoning (AA-LCR) 82.7 vs 80.7
- Ahead on 2 more benchmark figures
GPT-6 Astra
- Larger context window 1,050,000 tokens
- Higher physics research reasoning (CritPt) 31.7 vs 31.4
- Higher factual accuracy (Omniscience Accuracy) 62.6 vs 53.9
- Higher answer reliability (Omniscience Non-Hallucination) 55.2 vs 53
- Offers Flex and Priority pricing not listed for Claude Sonnet 5.5
What four workloads cost
One run, and the same run a thousand times.
Claude Sonnet 5.5 is cheaper on all four workloads, by much the same margin each time — about 6.5 times, from $0.0070 against $0.0350 on a chat turn to $0.8300 against $8.23 on a long document.
| Workload | Claude Sonnet 5.5 | GPT-6 Astra | ×1,000 | Difference |
|---|---|---|---|---|
| Chat turn 1,000 in / 500 out | $0.0070 | $0.0350 | $7.00 / $35.00 | Claude Sonnet 5.5 is 80% cheaper |
| RAG answer 10,000 in / 800 out | $0.0280 | $0.1400 | $28.00 / $140.00 | Claude Sonnet 5.5 is 80% cheaper |
| Agent loop 32,000 in / 700 out × 20 calls | $0.2800 | $1.70 | $280.00 / $1,700.00 | Claude Sonnet 5.5 is 84% cheaper |
| Long document 400,000 in / 3,000 out | $0.8300 | $8.23 | $830.00 / $8,225.00 | Claude Sonnet 5.5 is 90% cheaper |
Price per 1M tokens
Above 272,000 input tokens the rates change, and the new rate applies to the whole request, not just the tokens past that point: GPT-6 Astra's input goes from $10.00 to $20.00. It does not change which of the two is cheaper.
| Context band | Price | Claude Sonnet 5.5 | GPT-6 Astra | Difference |
|---|---|---|---|---|
| Prompts up to 272,000 tokens | Input | $2.00 | $10.00 | Claude Sonnet 5.5 is 80% cheaper |
| Prompts up to 272,000 tokens | Cached input | $0.10 | $1.00 | Claude Sonnet 5.5 is 90% cheaper |
| Prompts up to 272,000 tokens | Output | $10.00 | $50.00 | Claude Sonnet 5.5 is 80% cheaper |
| Prompts over 272,000 tokens | Input | $2.00 | $20.00 | Claude Sonnet 5.5 is 90% cheaper |
| Prompts over 272,000 tokens | Cached input | $0.10 | $2.00 | Claude Sonnet 5.5 is 95% cheaper |
| Prompts over 272,000 tokens | Output | $10.00 | $75.00 | Claude Sonnet 5.5 is 87% cheaper |
Blended: Claude Sonnet 5.5 $4.00, GPT-6 Astra $20.00 per 1M — one rate at 3:1 input to output, for comparing two models at a glance.
Claude Sonnet 5.5 priced by Anthropic, GPT-6 Astra by OpenAI. Standard tier, pay-as-you-go.
Other pricing tiers
Both models offer Batch, worth up to 50% off their standard rates, and the cheaper model is the same one on every tier — so the tier you buy changes the bill rather than the choice. Only GPT-6 Astra lists Flex and Priority, at up to 50% off its own standard rate; Claude Sonnet 5.5 offers none of them.
Every tier either model sells is here, so this is the whole price sheet. A saving is measured against that model's own standard rate — how we read tiers.
| Tier | Claude Sonnet 5.5 | GPT-6 Astra | Cheaper |
|---|---|---|---|
| Batch | $1.00 in / $5.00 out 50% off Standard | $5.00 in / $25.00 out 50% off Standard | Claude Sonnet 5.5 |
| Flex only on GPT-6 Astra | Not offered | $5.00 in / $25.00 out 50% off Standard | — |
| Priority only on GPT-6 Astra | Not offered | $20.00 in / $100.00 out | — |
Benchmarks
They share 8 figures: Claude Sonnet 5.5 leads on 5, GPT-6 Astra on 3. The widest gap is 13.3 points, on real-world task performance (GDPval).
Overall intelligence
Intelligence Index — Overall intelligence across reasoning, knowledge & math evals
Claude Sonnet 5.5 ahead by 3.3
Expert-exam performance
Humanity's Last Exam — Expert-level questions across many academic domains
Claude Sonnet 5.5 ahead by 0.3
Long-context reasoning
AA-LCR — Long-context reasoning across large inputs
Claude Sonnet 5.5 ahead by 2
Scientific coding
SciCode — Research-level scientific coding tasks
Claude Sonnet 5.5 ahead by 4.5
Physics research reasoning
CritPt — Unpublished physics research reasoning problems
GPT-6 Astra ahead by 0.3
Real-world task performance
GDPval — Economically valuable, real-world knowledge work
Claude Sonnet 5.5 ahead by 13.3
Factual accuracy
Omniscience Accuracy — Breadth of factual knowledge across domains
GPT-6 Astra ahead by 8.7
Answer reliability
Omniscience Non-Hallucination — How reliably the model avoids fabricated answers
GPT-6 Astra ahead by 2.2
Each figure is that model's best published run, with the effort level named beside it — where these scores come from.
Specifications
GPT-6 Astra holds 50,000 more input tokens in one request. Only GPT-6 Astra lists web search, code execution and computer use.
| Specification | Claude Sonnet 5.5 | GPT-6 Astra |
|---|---|---|
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Takes in | Text, image, file | Text, image, file |
| Puts out | Text | Text |
| Knowledge cutoff | — | 30 Apr 2026 |
| Released | 28 Sep 2026 | 3 Sep 2026 |
| Status | Active | Active |
| Sold by | Anthropic, Perplexity | OpenAI, Perplexity |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Web search | Not listed | Yes |
| Prompt caching | Yes | Yes |
| Code execution | Not listed | Yes |
| Computer use | Not listed | Yes |
| Open weights | Not listed | Not listed |
| Reasoning | Yes | Yes |
FAQs
- Is Claude Sonnet 5.5 cheaper than GPT-6 Astra?
- Yes. A 1,000-token prompt with a 500-token reply costs $0.0070 on Claude Sonnet 5.5 and $0.0350 on GPT-6 Astra, and the same model is cheaper on every workload on this page.
- How much do Claude Sonnet 5.5 and GPT-6 Astra cost per 1M tokens?
- Claude Sonnet 5.5 costs $2.00 for input and $10.00 for output. GPT-6 Astra costs $10.00 and $50.00. Standard pay-as-you-go rates, as of 8 Oct 2026.
- Which is better, Claude Sonnet 5.5 or GPT-6 Astra?
- On published benchmarks, Claude Sonnet 5.5. It leads on 5 of the 8 figures both models report, including overall intelligence (Intelligence Index), where it scores 56 against 52.7.
- Is Batch pricing cheaper for Claude Sonnet 5.5 or GPT-6 Astra?
- Batch input costs $1.00 on Claude Sonnet 5.5 and $5.00 on GPT-6 Astra, 50% below the standard rate on both.
- Does Claude Sonnet 5.5 or GPT-6 Astra have a bigger context window?
- GPT-6 Astra, at 1,050,000 tokens against 1,000,000. That is 50,000 more input tokens in a single request.