GPT-5.6 Luna vs GPT-6 Astra: pricing and benchmarks
GPT-5.6 Luna is 98% cheaper on input tokens ($0.20 vs $10.00 per 1M). GPT-5.6 Luna is 98% cheaper on output tokens ($1.20 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $5,500 for GPT-6 Astra, 98% less. GPT-6 Astra scores 166.3 on the Epoch Capabilities Index vs 156.3 for GPT-5.6 Luna.
Prices verified September 14, 2026.
Which should you choose?
GPT-6 Astra scores 166.3 on the Epoch Capabilities Index vs 156.3 for GPT-5.6 Luna.
GPT-6 Astra scores 74.1% on DeepSWE vs 67.2% for GPT-5.6 Luna.
GPT-6 Astra scores 93.7% on FrontierMath (Tiers 1–3) vs 82.1% for GPT-5.6 Luna.
GPT-5.6 Luna costs $0.45 per 1M tokens (3:1 input-to-output mix) vs $20.00 for GPT-6 Astra, 98% less.
A trade-off: GPT-6 Astra is 10.0 ECI points more capable but costs 44.4x as much as GPT-5.6 Luna.
Pricing and specs
| GPT-5.6 Luna | GPT-6 Astra | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| API model ID | gpt-5.6-luna | gpt-6-astra |
| Input / 1M tokens | $0.20 | $10.00 |
| Cached input / 1M tokens | $0.02 | $1.00 |
| Output / 1M tokens | $1.20 | $50.00 |
| Long-context rates | $0.40 in / $1.80 out on long-context requests | $20.00 in / $75.00 out on long-context requests |
| Context window | 1.05M tokens | 1.05M tokens |
| Max output | 128K tokens | 128K tokens |
| Batch discount | 50% off | 50% off |
Benchmarks
| GPT-5.6 Luna | GPT-6 Astra | |
|---|---|---|
| Epoch Capabilities Index | 156.3 | 166.3 |
| GPQA Diamond· Science reasoning | 88.8% | 94.4% |
| FrontierMath (Tiers 1–3)· Advanced math | 82.1% | 93.7% |
| SimpleQA Verified· Factual accuracy | 41.0% | 75.6% |
| ARC-AGI-2· Abstract reasoning | 59.5% | 95.0% |
| DeepSWE· Coding | 67.2% | 74.1% |
| APEX-Agents· Agentic work | — | 46.7% |
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 | GPT-5.6 Luna | GPT-6 Astra | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $78.00 | $3,500 | GPT-5.6 Luna 98% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $116.00 | $5,500 | GPT-5.6 Luna 98% 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. | $53.60 | $2,480 | GPT-5.6 Luna 98% 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.
GPT-5.6 Luna vs GPT-6 Astra cost calculator
- $116.00/mo$0.0023 / request
- GPT-6 AstraOpenAI$5,500/mo$0.11 / request
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
GPT-5.6 Luna pricing notes
The GPT-5.6 model optimized for cost-sensitive, high-volume workloads.
- Cache writes are billed at $0.25 per 1M tokens.
- Fast mode costs 2x the standard rate; Flex costs half.
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 GPT-5.6 Luna cheaper than GPT-6 Astra?
- GPT-5.6 Luna is 98% cheaper on input tokens ($0.20 vs $10.00 per 1M). GPT-5.6 Luna is 98% cheaper on output tokens ($1.20 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $5,500 for GPT-6 Astra, 98% less.
- Which is more capable, GPT-5.6 Luna or GPT-6 Astra?
- GPT-6 Astra scores 166.3 on the Epoch Capabilities Index vs 156.3 for GPT-5.6 Luna.
- How much does GPT-5.6 Luna cost per 1M tokens?
- GPT-5.6 Luna costs $0.20 per 1M input tokens and $1.20 per 1M output tokens, and $0.02 per 1M cached input tokens on OpenAI’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, GPT-5.6 Luna or GPT-6 Astra?
- Both offer a 1.05M-token context window.