Kimi K3 is Moonshot's open-weights agentic model; GPT-6 Astra is OpenAI's top flagship. Both take roughly a million tokens of context, at very different prices — especially past 272K tokens.
Kimi K3 costs about a third of GPT-6 Astra per input and output token, and its cache hits are a third of Astra's too. On prompts above 272K tokens Astra's rate goes up, widening the gap further. Astra makes sense when you need OpenAI's platform or your evals justify the premium.
| Kimi K3 | GPT-6 Astra | |
|---|---|---|
| Provider | Moonshot AI | OpenAI |
| Tier | Flagship | Flagship |
| Input / 1M tokens | $3.00 | $10.00 |
| Output / 1M tokens | $15.00 | $50.00 |
| Cache hit / 1M | $0.30 | $1.00 |
| Cache write / 1M | $3.00 | $12.50 |
| Context window | 1M | 1M |
| Notes | Previous-generation flagship, superseded by Kimi K3.1 Pro but still sold; open weights; cache write $3 (5-min TTL) or $6 (1-h TTL) | New top flagship (Sep 3, 2026); rolling out to Plus/Pro/Business/Enterprise; >272K tokens: $20/$75, cache $2 |
Kimi K3 is 3.3× cheaper on input tokens ($3.00 vs $10.00 per 1M). Kimi K3 is 3.3× cheaper on output tokens ($15.00 vs $50.00 per 1M).
| Workload | Kimi K3 | GPT-6 Astra | Difference |
|---|---|---|---|
| Support chatbot 10,000 conversations × (2,000 input + 400 output tokens) | $120 | $400 | Kimi K3 saves $280 |
| Document Q&A 1,000 questions × (30,000 input + 800 output tokens) | $102 | $340 | Kimi K3 saves $238 |
| Coding agent session 4M input tokens (90% cache hits) + 150,000 output tokens | $4.53 | $15.10 | Kimi K3 saves $10.57 |
Standard rates per 1M tokens from data on this site. The coding-agent row assumes 90% of input is read from the prompt cache (full input price where a model has no cache rate). Cache-write fees, batch discounts and long-context surcharges listed in the notes are not included. Updated November 2, 2026.
you want open weights, run long agent loops where its $0.30 cache-hit rate applies, or send prompts above 272K tokens without a surcharge.
your stack depends on OpenAI's API, tools and SDKs, or your own testing shows Astra solving your tasks with fewer retries.
Moonshot lists a 1,048,576-token window for the K3 series and no long-context price tier. Astra moves to 2× input and 1.5× output above 272K tokens, so a 400K-token prompt costs proportionally more on Astra than the headline ratio implies.
Kimi K3 caches repeated prefixes automatically and bills cache writes separately by TTL; Astra charges $12.50 per 1M tokens to write a 30-minute cache. For non-urgent jobs, Moonshot's batch inference for kimi-k3 is 60% of standard price, while OpenAI's Batch and Flex tiers are 50%. Batched Astra is still well above batched Kimi K3.
Kimi K3's open weights mean you are not locked into one API vendor: you can move it to your own hardware or another inference host if prices or terms change. GPT-6 Astra is only available through OpenAI.
Roughly 3× on input, output and cache hits at standard rates, and more on prompts above 272K tokens, where Astra's rate rises.
Yes, Kimi K3 is an open-weights model. GPT-6 Astra is API-only.
Moonshot lists 1,048,576 tokens for all K3 series models.
How we choose: prices come from each vendor's official pricing page and are re-checked every week. We take no affiliate fees, so rankings aren't for sale.