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GPT-6 Luna vs Grok 4.3
Price, context window and capabilities side by side, read from the same catalog that meters your calls, not from a press release.
GPT-6 Luna is 13x cheaper on input. GPT-6 Luna is 5.0x cheaper on output. GPT-6 Luna holds 1.1M tokens against 1M.
At a glance
Side by side
OpenAI
GPT-6's high-volume tier: the cheapest frontier-family model in the catalog, with a million-token window.
Specifications
Every difference we can measure
| GPT-6 Luna | Grok 4.3 | |
|---|---|---|
| Input price | $0.1/M | $1.25/M |
| Output price | $0.5/M | $2.5/M |
| Context window | 1.1M tokens | 1M tokens |
| Vision | Yes | No |
| Tool calling | Yes | Yes |
| Prompt caching | Yes | No |
| Long context | Yes | Yes |
A row appears only when we hold the fact for both models. Anything the provider has not published is left out rather than guessed, so an empty row is missing data and never a zero.
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FAQ
Frequently asked questions
What is the difference between GPT-6 Luna and Grok 4.3?
GPT-6 Luna is 13x cheaper on input. GPT-6 Luna is 5.0x cheaper on output. GPT-6 Luna holds 1.1M tokens against 1M. Only GPT-6 Luna declares vision. Only GPT-6 Luna declares prompt caching. Both run on the same endpoint and the same key here, so trying each is a one-line change to the model id.
Which is cheaper, GPT-6 Luna or Grok 4.3?
GPT-6 Luna is, on input tokens. Output usually dominates the bill on generative work, so check the output row above against your own ratio of prompt to completion before deciding.
Can I switch between GPT-6 Luna and Grok 4.3 without changing my code?
Yes. Both are OpenAI-compatible through one CompanyFabric key, so switching is the model string and nothing else, no second SDK, no second contract, one prepaid balance across both.
Do I have to choose?
No. Send companyfabric/auto and we route each request to the cheapest model that can serve it, which is how most people use both without deciding in advance.
One key. Every model. Exact prices.
Run GPT-6 Luna and Grok 4.3 on the same key and compare them on your own prompts. Free starter credits included, no subscription required.