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GPT-6 Astra vs GPT-5.5
A straight cost comparison of GPT-6 Astra (OpenAI) and GPT-5.5 (OpenAI), per 1,000,000 tokens, verified October 2026.
Rate-by-rate comparison
| Metric | GPT-6 Astra | GPT-5.5 | Winner |
|---|---|---|---|
| Input / 1M | $10 | $5 | GPT-5.5 |
| Cached input / 1M | $1 | $0.50 | GPT-5.5 |
| Cache write / 1M | $12.50 | — | GPT-5.5 |
| Output / 1M | $50 | $30 | GPT-5.5 |
| Context window | 1,050,000 | 1,050,000 | Tie |
| Batch API | Yes | Yes | Tie |
| Long-context tier | > 272,000 | > 272,000 | — |
For per-token metrics, the lower number wins. For context window and batch support, the higher or broader option wins. A dash means the provider does not publish that rate: a missing cache-write fee means writes are not billed per token, while a missing cached-input rate means cache hits bill at the full input rate.
Blended cost: 1M input + 250K output
| Model | Blended cost | Difference |
|---|---|---|
| GPT-6 Astra | $22.50 | +$10 |
| GPT-5.5 | $12.50 | Cheaper |
Three workloads, two bills
| Workload | GPT-6 Astra | GPT-5.5 | Winner |
|---|---|---|---|
| Support chat 1,000 requests · 4K input / 600 output | $70 | $38 | GPT-5.5 |
| RAG with caching 1,000 requests · 50K input (45K cached) / 1K output | $146 | $77.70 | GPT-5.5 |
| Nightly batch job 10,000 requests · 10K input / 2K output | $1000 | $550 | GPT-5.5 |
Which one should you pick?
GPT-6 Astra wins on none of the three workloads above, while GPT-5.5 wins on support chat, cached RAG, nightly batch job.
Beyond price, the two differ on input rate ($10 vs $5); output rate ($50 vs $30); cached-input rate ($1 vs $0.50); cache-write rate ($12.50 vs —).
Batch mode is available on GPT-6 Astra and GPT-5.5, which halves the nightly job. Both publish cached-input discounts, so a stable system prompt is worth caching on either.
FAQ
Is GPT-6 Astra cheaper than GPT-5.5?
On a blended 1M-input-plus-250K-output workload, GPT-5.5 is cheaper by 44% ($12.50 vs $22.50). The gap changes for cache-heavy prompts and for batch jobs, as the workload table shows.
Which handles longer prompts, GPT-6 Astra or GPT-5.5?
Both models share the same 1,050,000-token context window. Watch the long-context threshold on GPT-6 Astra and GPT-5.5: rates rise once input passes it.
Do both models support prompt caching?
GPT-6 Astra bills cached reads at $1 per 1M; GPT-5.5 at $0.50.