GPT-6 Luna vs Grok 4.3: pricing and benchmarks
GPT-6 Luna is 92% cheaper on input tokens ($0.10 vs $1.25 per 1M). GPT-6 Luna is 80% cheaper on output tokens ($0.50 vs $2.50 per 1M). On our document Q&A workload (50,000 questions a month), GPT-6 Luna costs $55.00 a month versus $575.00 for Grok 4.3, 90% less. Epoch AI has not published a capability index score for GPT-6 Luna and Grok 4.3 yet.
Prices verified September 26, 2026.
Which should you choose?
Epoch AI has not published a capability index score for GPT-6 Luna and Grok 4.3 yet.
GPT-6 Luna costs $0.20 per 1M tokens (3:1 input-to-output mix) vs $1.563 for Grok 4.3, 87% less.
Pricing and specs
| GPT-6 Luna | Grok 4.3 | |
|---|---|---|
| Provider | OpenAI | xAI |
| API model ID | gpt-6-luna | grok-4.3 |
| Input / 1M tokens | $0.10 | $1.25 |
| Cached input / 1M tokens | $0.01 | $0.20 |
| Output / 1M tokens | $0.50 | $2.50 |
| Long-context rates | $0.20 in / $0.75 out on long-context requests | $2.50 in / $5.00 out above 200K prompt tokens |
| Context window | 1.05M tokens | 1M tokens |
| Max output | 128K tokens | — |
| Batch discount | 50% off | — |
Monthly cost for real workloads
| Workload | GPT-6 Luna | Grok 4.3 | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $35.00 | $287.50 | GPT-6 Luna 88% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $55.00 | $575.00 | GPT-6 Luna 90% 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. | $24.80 | $256.00 | GPT-6 Luna 90% 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-6 Luna vs Grok 4.3 cost calculator
- $55.00/mo$0.0011 / request
- Grok 4.3xAI$575.00/mo$0.01 / 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-6 Luna pricing notes
OpenAI’s most efficient GPT-6 model, for focused, high-volume tasks.
- Cache writes are billed at $0.125 per 1M tokens.
- Fast mode costs 2x the standard rate; Flex costs half.
- Regional (data residency) endpoints add a 10% uplift, and EU data residency is available only with standard processing.
Grok 4.3 pricing notes
An earlier Grok 4 model with a 1M-token context window.
- Requests with 200K or more prompt tokens are billed at $2.50 input / $0.40 cached / $5 output for all tokens.
Frequently asked questions
- Is GPT-6 Luna cheaper than Grok 4.3?
- GPT-6 Luna is 92% cheaper on input tokens ($0.10 vs $1.25 per 1M). GPT-6 Luna is 80% cheaper on output tokens ($0.50 vs $2.50 per 1M). On our document Q&A workload (50,000 questions a month), GPT-6 Luna costs $55.00 a month versus $575.00 for Grok 4.3, 90% less.
- Which is more capable, GPT-6 Luna or Grok 4.3?
- Epoch AI has not published a capability index score for GPT-6 Luna and Grok 4.3 yet.
- How much does GPT-6 Luna cost per 1M tokens?
- GPT-6 Luna costs $0.10 per 1M input tokens and $0.50 per 1M output tokens, and $0.01 per 1M cached input tokens on OpenAI’s standard tier.
- How much does Grok 4.3 cost per 1M tokens?
- Grok 4.3 costs $1.25 per 1M input tokens and $2.50 per 1M output tokens, and $0.20 per 1M cached input tokens on xAI’s standard tier.
- Which has the larger context window, GPT-6 Luna or Grok 4.3?
- GPT-6 Luna has the larger context window: 1.05M tokens versus 1M for Grok 4.3.