GPT-6.1 Terra vs Gemini 3.8 Flash
Gemini 3.8 Flash is 1.3x cheaper than GPT-6.1 Terra on our example workload, at list prices.
Side by side
| GPT-6.1 Terra | Gemini 3.8 Flash | |
|---|---|---|
| Provider | OpenAI | |
| Input / 1M tokens | $1.00 | $0.750 |
| Output / 1M tokens | $5.00 | $3.75 |
| Output price ÷ input price | 5.0x | 5.0x |
| Blended / 1M (3:1) | $2.00 | $1.50 |
| Context window | 1.05M | 1M |
| ≈ English words that fit | 788,000 | 750,000 |
| 1,000 calls (2000+500 tok) | $4.50 | $3.38 |
| AA Intelligence Index | 51 | 31 |
| LMArena Text | n/a | 1496 |
| Blended $ per AA index point | $0.039 | $0.048 |
List prices from official pages (OpenAI, Google), verified 2026-11-04. Benchmarks from public leaderboards (Artificial Analysis, LMArena), not run by us. Word counts use the rough 0.75 words per token rule for English. "$ per index point" is our own arithmetic (blended price ÷ index score), a rough value-for-money signal, not a benchmark.
What real workloads cost
Four example request shapes, priced at list rates with no caching or batch discounts. Monthly figures assume 100,000 requests.
| Workload | GPT-6.1 Terra | Gemini 3.8 Flash | Gap |
|---|---|---|---|
| Support chat reply a short system prompt, recent chat history and a reply | $0.00450 each $450.00 / mo | $0.00337 each $337.50 / mo | 1.3x |
| RAG answer a question plus about 20K tokens of retrieved documents, and a cited answer | $0.0240 each $2,400.00 / mo | $0.0180 each $1,800.00 / mo | 1.3x |
| 10-step agent task an agent loop of 10 model calls, each re-reading about 8K tokens of context and emitting a 400-token tool call | $0.1000 each $10,000.00 / mo | $0.0750 each $7,500.00 / mo | 1.3x |
| Long-report summary one 200K-token document summarized into about 2K tokens | $0.2100 each $21,000.00 / mo | $0.1575 each $15,750.00 / mo | 1.3x |
When to pick each
- Pick Gemini 3.8 Flash when cost is the main constraint: at list prices it is 1.3x cheaper than GPT-6.1 Terra on a typical 2,000-in / 500-out call ($3.38 vs $4.50 per 1,000 calls).
- Pick GPT-6.1 Terra when answer quality matters more than price: it scores 51 vs 31 on the Artificial Analysis Intelligence Index, and costs 1.3x more per call.
- Pick GPT-6.1 Terra if a single prompt can exceed 1M tokens (about 750,000 English words): its window is 1.05M.
- They come from different providers (OpenAI and Google), so switching means a second API key, SDK and billing account, and tool-calling formats differ. Our schema converter outputs both formats from one JSON Schema.
Context and pricing limits
- GPT-6.1 Terra: 1.05M tokens of context. Gemini 3.8 Flash: 1M. GPT-6.1 Terra holds 1.1x more.
- GPT-6.1 Terra: Short-context (<=272K input) price. The prices above are this tier; check the official pricing page before committing.
- Gemini 3.8 Flash: Promo price through Dec 31, 2026; $1.50/$7.50 from Jan 1, 2027. The prices above are this tier; check the official pricing page before committing.
- Cached input, batch and off-peak discounts can cut real bills a lot and differ by provider; they are not included here.
FAQ
Is Gemini 3.8 Flash cheaper than GPT-6.1 Terra?
Yes, on our 2000-in / 500-out example call it costs $0.00337 vs $0.00450, 1.3x less.
Which has the larger context window?
GPT-6.1 Terra, with 1.05M tokens vs 1M.
Which scores higher on benchmarks?
GPT-6.1 Terra scores 51 vs 31 on the Artificial Analysis Intelligence Index. LMArena Text: GPT-6.1 Terra n/a, Gemini 3.8 Flash 1496. Benchmarks are averages; test both on your own prompts.
Run your own numbers in the token cost estimator · GPT-6.1 Terra pricing · Gemini 3.8 Flash pricing · All comparisons