GPT-5.6 Luna vs Grok 4.6: pricing and benchmarks
GPT-5.6 Luna is 90% cheaper on input tokens ($0.20 vs $2.00 per 1M). GPT-5.6 Luna is 80% cheaper on output tokens ($1.20 vs $6.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $980.00 for Grok 4.6, 88% less. Roughly tied. GPT-5.6 Luna scores 156.3 and Grok 4.6 scores 156.3 on the Epoch Capabilities Index, and their confidence intervals overlap.
Prices verified September 14, 2026.
Which should you choose?
Roughly tied. GPT-5.6 Luna scores 156.3 and Grok 4.6 scores 156.3 on the Epoch Capabilities Index, and their confidence intervals overlap.
About even on DeepSWE: 67.2% for GPT-5.6 Luna and 67.5% for Grok 4.6.
GPT-5.6 Luna scores 82.1% on FrontierMath (Tiers 1–3) vs 66.0% for Grok 4.6.
GPT-5.6 Luna costs $0.45 per 1M tokens (3:1 input-to-output mix) vs $3.00 for Grok 4.6, 85% less.
GPT-5.6 Luna delivers statistically similar overall capability for 85% less.
Pricing and specs
| GPT-5.6 Luna | Grok 4.6 | |
|---|---|---|
| Provider | OpenAI | xAI |
| API model ID | gpt-5.6-luna | grok-4.6 |
| Input / 1M tokens | $0.20 | $2.00 |
| Cached input / 1M tokens | $0.02 | $0.50 |
| Output / 1M tokens | $1.20 | $6.00 |
| Long-context rates | $0.40 in / $1.80 out on long-context requests | $4.00 in / $12.00 out above 200K prompt tokens |
| Context window | 1.05M tokens | 500K tokens |
| Max output | 128K tokens | — |
| Batch discount | 50% off | — |
Benchmarks
| GPT-5.6 Luna | Grok 4.6 | |
|---|---|---|
| Epoch Capabilities Index | 156.3 | 156.3 |
| GPQA Diamond· Science reasoning | 88.8% | 92.0% |
| FrontierMath (Tiers 1–3)· Advanced math | 82.1% | 66.0% |
| SimpleQA Verified· Factual accuracy | 41.0% | 49.3% |
| ARC-AGI-2· Abstract reasoning | 59.5% | 67.1% |
| DeepSWE· Coding | 67.2% | 67.5% |
| APEX-Agents· Agentic work | — | 41.2% |
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 | Grok 4.6 | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $78.00 | $540.00 | GPT-5.6 Luna 86% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $116.00 | $980.00 | GPT-5.6 Luna 88% 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 | $500.00 | GPT-5.6 Luna 89% 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 Grok 4.6 cost calculator
- $116.00/mo$0.0023 / request
- Grok 4.6xAI$980.00/mo$0.02 / 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.
Grok 4.6 pricing notes
xAI’s flagship model for code and everything else, with agentic tool calling and configurable reasoning.
- Requests with 200K or more prompt tokens are billed at $4 input / $1 cached / $12 output for all tokens.
- Web Search and X Search tools cost $5 per 1,000 calls.
Frequently asked questions
- Is GPT-5.6 Luna cheaper than Grok 4.6?
- GPT-5.6 Luna is 90% cheaper on input tokens ($0.20 vs $2.00 per 1M). GPT-5.6 Luna is 80% cheaper on output tokens ($1.20 vs $6.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $980.00 for Grok 4.6, 88% less.
- Which is more capable, GPT-5.6 Luna or Grok 4.6?
- Roughly tied. GPT-5.6 Luna scores 156.3 and Grok 4.6 scores 156.3 on the Epoch Capabilities Index, and their confidence intervals overlap.
- 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 Grok 4.6 cost per 1M tokens?
- Grok 4.6 costs $2.00 per 1M input tokens and $6.00 per 1M output tokens, and $0.50 per 1M cached input tokens on xAI’s standard tier.
- Which has the larger context window, GPT-5.6 Luna or Grok 4.6?
- GPT-5.6 Luna has the larger context window: 1.05M tokens versus 500K for Grok 4.6.