Claude Sonnet 5.5 vs GPT-6 Astra: pricing and benchmarks
Claude Sonnet 5.5 is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Claude Sonnet 5.5 is 80% cheaper on output tokens ($10.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Claude Sonnet 5.5 costs $1,100 a month versus $5,500 for GPT-6 Astra, 80% less. Roughly tied. Claude Sonnet 5.5 scores 164.4 and GPT-6 Astra scores 166.4 on the Epoch Capabilities Index, and their confidence intervals overlap.
Which should you choose?
Roughly tied. Claude Sonnet 5.5 scores 164.4 and GPT-6 Astra scores 166.4 on the Epoch Capabilities Index, and their confidence intervals overlap.
GPT-6 Astra scores 93.7% on FrontierMath (Tiers 1–3) vs 88.8% for Claude Sonnet 5.5.
Claude Sonnet 5.5 costs $4.00 per 1M tokens (3:1 input-to-output mix) vs $20.00 for GPT-6 Astra, 80% less.
Claude Sonnet 5.5 delivers statistically similar overall capability for 80% less.
Pricing and specs
| Claude Sonnet 5.5 | GPT-6 Astra | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| API model ID | claude-sonnet-5-5 | gpt-6-astra |
| Input / 1M tokens | $2.00 | $10.00 |
| Cached input / 1M tokens | $0.20 | $1.00 |
| Output / 1M tokens | $10.00 | $50.00 |
| Long-context rates | — | $20.00 in / $75.00 out on long-context requests |
| Context window | 1M tokens | 1.05M tokens |
| Max output | 128K tokens | 128K tokens |
| Batch discount | 50% off | 50% off |
Benchmarks
| Claude Sonnet 5.5 | GPT-6 Astra | |
|---|---|---|
| Epoch Capabilities Index | 164.4 | 166.4 |
| GPQA Diamond· Science reasoning | 95.6% | 95.8% |
| FrontierMath (Tiers 1–3)· Advanced math | 88.8% | 93.7% |
| SimpleQA Verified· Factual accuracy | 46.5% | 75.6% |
| ARC-AGI-2· Abstract reasoning | — | 95.0% |
| DeepSWE· Coding | — | 74.1% |
| APEX-Agents· Agentic work | 75.5% | 64.7% |
Source: Epoch AI, best recorded result per model (CC BY 4.0). A dash means no published score. See all benchmarks
Monthly cost for real workloads
| Workload | Claude Sonnet 5.5 | GPT-6 Astra | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $700.00 | $3,500 | Claude Sonnet 5.5 80% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $1,100 | $5,500 | Claude Sonnet 5.5 80% cheaper |
Coding agent 10,000 agent steps a month, ~40,000 input tokens each (70% read from the prompt cache) and ~2,000 output tokens. | $496.00 | $2,480 | Claude Sonnet 5.5 80% cheaper |
Cached chatbot The same 100,000-reply support chatbot, but 60% of each prompt (system prompt + conversation history) is served from the prompt cache. | $538.00 | $2,690 | Claude Sonnet 5.5 80% cheaper |
Meeting notes 10,000 meetings a month summarized from ~12,000-token transcripts, ~1,000 output tokens each. | $340.00 | $1,700 | Claude Sonnet 5.5 80% cheaper |
Bulk translation 200,000 short translations a month, ~800 input and ~800 output tokens each. | $1,920 | $9,600 | Claude Sonnet 5.5 80% cheaper |
Content moderation 1,000,000 classifications a month, ~400 input tokens and ~80 output tokens each. | $1,600 | $8,000 | Claude Sonnet 5.5 80% cheaper |
Article drafting 300 long-form articles a month written from a ~4,000-token brief and outline, ~5,000 output tokens each. | $17.40 | $87.00 | Claude Sonnet 5.5 80% cheaper |
Code review bot 30,000 pull-request reviews a month, ~5,000 input tokens each (30% cached repository context) and ~700 output tokens. | $429.00 | $2,145 | Claude Sonnet 5.5 80% cheaper |
Invoice extraction 100,000 documents a month parsed into structured JSON, ~1,200 input and ~250 output tokens each. | $490.00 | $2,450 | Claude Sonnet 5.5 80% cheaper |
Estimates use standard list prices and ignore cache-write surcharges. Different tokenizers can count the same text differently, so test with your own prompts.
Claude Sonnet 5.5 vs GPT-6 Astra cost calculator
- $1,100/mo$0.02 / req
- GPT-6 AstraOpenAI$5,500/mo$0.11 / req
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
Claude Sonnet 5.5 pricing notes
Anthropic’s fast mid-tier model, successor to Claude Sonnet 5 at the same price.
- Cache writes cost $2.50 (5-minute cache) or $4 (1-hour cache) per 1M tokens.
- US-only inference (inference_geo: "us") costs 1.1x.
GPT-6 Astra pricing notes
OpenAI’s most capable model, built for the hardest end-to-end reasoning and coding work.
- Cache writes are billed at $12.50 per 1M tokens.
- Fast mode costs 2x the standard rate; Flex costs half.
- Regional (data residency) endpoints add a 10% uplift.
Frequently asked questions
- Is Claude Sonnet 5.5 cheaper than GPT-6 Astra?
- Claude Sonnet 5.5 is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Claude Sonnet 5.5 is 80% cheaper on output tokens ($10.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Claude Sonnet 5.5 costs $1,100 a month versus $5,500 for GPT-6 Astra, 80% less.
- Which is more capable, Claude Sonnet 5.5 or GPT-6 Astra?
- Roughly tied. Claude Sonnet 5.5 scores 164.4 and GPT-6 Astra scores 166.4 on the Epoch Capabilities Index, and their confidence intervals overlap.
- How much does Claude Sonnet 5.5 cost per 1M tokens?
- Claude Sonnet 5.5 costs $2.00 per 1M input tokens and $10.00 per 1M output tokens, and $0.20 per 1M cached input tokens on Anthropic’s standard tier.
- How much does GPT-6 Astra cost per 1M tokens?
- GPT-6 Astra costs $10.00 per 1M input tokens and $50.00 per 1M output tokens, and $1.00 per 1M cached input tokens on OpenAI’s standard tier.
- Which has the larger context window, Claude Sonnet 5.5 or GPT-6 Astra?
- GPT-6 Astra has the larger context window: 1.05M tokens versus 1M for Claude Sonnet 5.5.