GPT-5.6 Luna vs Grok 3
Pricing verdict: GPT-5.6 Luna vs Grok 3: GPT-5.6 Luna is cheaper for input-heavy usage ($1.00/M vs $3.00/M input tokens), while GPT-5.6 Luna is better for long-context tasks (1,050,000 tokens).
Direct answer: choose GPT-5.6 Luna for lower token spend and choose GPT-5.6 Luna when your workload needs longer context.
Compare API pricing, input and output token costs, context windows, and monthly estimates on one page so you can pick the right model fast.
Cost Comparison (1000 input + 500 output tokens, 100 requests/day)
GPT-5.6 Luna
Grok 3
Cost Differences
Grok 3 costs more than GPT-5.6 Luna
Quick Recommendation
Winner for direct API pricing: GPT-5.6 Luna. At the default workload, GPT-5.6 Luna saves about $19.50/month ($237.25/year) versus Grok 3.
Feature Comparison
| Feature | GPT-5.6 Luna | Grok 3 |
|---|---|---|
| Provider | OpenAI | xAI |
| Input Price | $1.00/1M tokens | $3.00/1M tokens |
| Output Price | $6.00/1M tokens | $15.00/1M tokens |
| Context Window | 1,050,000 tokens | 131,072 tokens |
| Max Output | 128,000 tokens | 131,072 tokens |
| Category | efficient | flagship |
| Capabilities | textvisioncodereasoning | textvisionreasoningcode |
| Release Date | 6/26/2026 | 2/17/2025 |
GPT-5.6 Luna vs Grok 3: Which Should You Choose?
Choosing between GPT-5.6 Luna and Grok 3 depends on your priorities: cost efficiency, context length, or raw capability. GPT-5.6 Luna is the more affordable option at $1.00/1M input tokens — 67% cheaper than Grok 3. Meanwhile, GPT-5.6 Luna offers a significantly larger context window at 1,050,000 tokens vs 131,072 for Grok 3.
These models come from different providers — OpenAI and xAI — which means different API ecosystems, SDKs, rate limits, and terms of service. If you're already integrated with OpenAI, switching to xAIinvolves migration effort beyond just pricing. Factor in your existing infrastructure when deciding.
These models target different tiers: GPT-5.6 Luna is a efficient model while Grok 3 is flagship. This means they're optimized for different workloads. Grok 3 targets more demanding workloads, while GPT-5.6 Luna provides a cost-effective option for everyday tasks.
Output costs matter too. GPT-5.6 Luna charges $6.00/1M output tokens vs $15.00 for Grok 3. For generation-heavy workloads (content creation, code generation, summarization), output pricing often dominates your bill. GPT-5.6 Luna has the edge here at $6.00/1M output tokens.
Multimodal capabilities: Both models support vision (image understanding), so you can send images alongside text prompts with either option.
Best Use Cases
Choose GPT-5.6 Luna when:
- • Budget is a primary concern
- • You need a larger context window (1,050,000 tokens)
- • You're already using OpenAI's API ecosystem
- • You're running high-volume, latency-sensitive workloads
Choose Grok 3 when:
- • You need longer outputs (up to 131,072 tokens)
- • You're already using xAI's API ecosystem
Pros and Caveats at a Glance
GPT-5.6 Luna
- • Input pricing: $1.00/M tokens
- • Output pricing: $6.00/M tokens
- • Context window: 1,050,000 tokens
- • Max output: 128,000 tokens
Watch out for
- • Trade-offs are minor in this matchup.
Grok 3
- • Input pricing: $3.00/M tokens
- • Output pricing: $15.00/M tokens
- • Context window: 131,072 tokens
- • Max output: 131,072 tokens
Watch out for
- • Higher input cost than GPT-5.6 Luna
- • Higher output cost than GPT-5.6 Luna
- • Smaller context window than GPT-5.6 Luna
Try Different Scenarios
Use the calculator below to see how costs change with different usage patterns
GPT-5.6 Luna (OpenAI)
Grok 3 (xAI)
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Sign Up for xAI →Frequently Asked Questions
Which is cheaper, GPT-5.6 Luna or Grok 3?▼
What is the context window difference between GPT-5.6 Luna and Grok 3?▼
Which model is better for AI Agent / Agentic Workflows?▼
Which model has better overall pricing for heavy usage?▼
Where can I compare OpenAI and xAI API pricing beyond this model matchup?▼
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