Grok 4.3 vs GPT-5.6 Luna
xAI vs OpenAI · Prices checked 12 August 2026
GPT-5.6 Luna is the cheaper of the two by a wide margin: $0.500 per million tokens blended against $1.63, roughly 3.3× less. A single 100K-input, 10K-output job costs $0.032 on GPT-5.6 Luna against $0.150 on Grok 4.3.
GPT-5.6 Luna takes a 1,050,000-token context window against 1,000,000, giving a modest edge for long documents or whole-codebase work. Grok 4.3 was released Apr 2026; GPT-5.6 Luna Jul 2026.
Pricing and capacity
| Metric | Grok 4.3 | GPT-5.6 Luna | Difference |
|---|---|---|---|
| Input / 1M tokens | $1.25 | $0.200 | 6.3× |
| Output / 1M tokens | $2.50 | $1.20 | 2.1× |
| Blended · 70/30calculated | $1.63 | $0.500 | 3.3× |
| Blended · 50/50calculated | $1.88 | $0.700 | 2.7× |
| Blended · 80/20calculated | $1.50 | $0.400 | 3.8× |
| Blended · 20/80calculated | $2.25 | $1.00 | 2.3× |
| Job cost · 100K + 10Kcalculated | $0.150 | $0.032 | 4.7× |
| Job cost · 1M + 100Kcalculated | $1.50 | $0.320 | 4.7× |
| Context window | 1,000,000 | 1,050,000 | 5% |
Input and output rates are as published by each provider. Blended and job-cost rows are calculated comparison metrics, not published prices — how they are derived.
Benchmarks
These two models do not currently report scores on any of the same benchmark suites, so there is no like-for-like capability comparison to show. Rather than pad the page with one-sided numbers, the benchmark leaderboards list every score we do hold.
What each model is for
Grok 4.3
xAI · Frontier
xAI's current flagship, fully rolled out to the API at the end of April 2026 at $1.25/$2.50 per MTok, roughly 40% below its predecessor on input and 60% on output. It adds native video input, document generation for PDFs, spreadsheets and slides, improved tool-calling, and three adjustable reasoning-intensity levels, alongside a 1M-token context window.
- Aggressive pricing for a flagship tier
- Native video input
- Document generation (PDF, spreadsheet, slides)
- Three adjustable reasoning-intensity levels
GPT-5.6 Luna
OpenAI · Efficient
The fastest and most affordable GPT-5.6 tier, a deliberately low-reasoning lane for high-volume work where speed and cost are the binding constraints rather than depth. It keeps the family's 1M-token context window at $0.20/$1.20 per MTok, which is 25× cheaper than Sol on input, with cached input at $0.02.
- Lowest cost in the GPT-5.6 family, 25× cheaper input than Sol
- Fast responses
- High-volume throughput
- 1M-token context
Frequently asked questions
Which is cheaper, Grok 4.3 or GPT-5.6 Luna?
GPT-5.6 Luna is the cheaper of the two by a wide margin: $0.500 per million tokens blended against $1.63, roughly 3.3× less. A single 100K-input, 10K-output job costs $0.032 on GPT-5.6 Luna against $0.150 on Grok 4.3. Blended cost weights input at 70% and output at 30%; price your own token split for an exact answer, since the cheaper model on a blended basis is not always cheaper for your workload.
Which has the larger context window, Grok 4.3 or GPT-5.6 Luna?
GPT-5.6 Luna takes a 1,050,000-token context window against 1,000,000, giving a modest edge for long documents or whole-codebase work. The context window caps everything in a single request: prompt, retrieved documents, conversation history and the model’s own output all share it.
Can I compare Grok 4.3 and GPT-5.6 Luna on my own numbers?
Yes. Open both in the side-by-side comparison tool to see every field at once, or use the token calculator to price your actual prompt and monthly request volume against each model. Both are free and need no sign-up.
Price it for your own workload
Related matchups
Terms used on this page
Prices and scores are recomputed on every deploy from the catalogue. Prices checked 12 August 2026.