GPT-5.6 Terra vs Gemini 3.8 Flash
Gemini 3.8 Flash is the better buy: the AIGROW small-business benchmark cannot tell the two apart, and Gemini 3.8 Flash has the lower list price. GPT-5.6 Terra passed 16 of 20 tasks and costs $2 in and $12 out per million tokens; Gemini 3.8 Flash passed 18 and costs $0.75 in and $3.75 out.
AIGROW credit covers Claude Opus 5.5, Claude Fable 5.2, Claude Fable 5.1, GPT-6 Astra, Claude Sonnet 5.5, GPT-6.1 Sol, GPT-6.1 Terra, Grok 4.7 and Gemini 4 Argon. GPT-6.1 Sol below list price
$25 a month brings $110 of API credit and cancels any time; $25 once buys $100. US dollars, standard rate, shortest context band. Cost per pass from the AIGROW small-business benchmark. Newer comparison: GPT-6.1 Terra vs Gemini 3.8 Flash
- GPT-5.6 Terra
- $6.68
- Tasks passed
- 16 of 20
- Gemini 3.8 Flash
- $7.17
- Tasks passed
- 18 of 20
AIGROW small-business benchmark, failed runs included.
OpenAI's GPT-5.6 mid tier against Google's workhorse, a common shortlist for high-volume business tasks. GPT-5.6 Terra costs $6.68 per 1,000 passing answers on the AIGROW small-business benchmark, Gemini 3.8 Flash $7.17. 1,000 support replies cost $10.80 on GPT-5.6 Terra and $3.75 on Gemini 3.8 Flash, so GPT-5.6 Terra costs 2.9 times as much.
What each one costs
The API price per million tokens and the cheapest app plan with each model, from the makers’ own pages. Each name opens that model’s full price page.
- GPT-5.6 Terra
- On the OpenAI API, GPT-5.6 Terra costs $2 per million input tokens and $12 per million output tokens. In ChatGPT, it comes with the free plan, and the cheapest paid plan with it is Go at $8/mo. Plan prices read 14 October 2026.
- Gemini 3.8 Flash
- On the Google API, Gemini 3.8 Flash costs $0.75 per million input tokens and $3.75 per million output tokens.
Side by side
Each maker’s published rate for its standard tier. Cached input is what a repeated prompt prefix costs once the provider has stored it.
| Fact | GPT-5.6 Terra | Gemini 3.8 Flash |
|---|---|---|
| Maker | OpenAI | |
| Tier | Workhorses | Workhorses |
| Input, per M tokens | $2.00 | $0.75 |
| Output, per M tokens | $12.00 | $3.75 |
| Cached input | $0.20 | $0.075 |
| Context window | 1.05M | 1.05M |
| Released | 9 Jul 2026 | 2 Sep 2026 |
| Weights | Closed weights | Closed weights |
What a job costs on each
1,000 runs of each job at the two list prices. The gap moves from job to job because the models price input, output and cached context differently.
| Job | GPT-5.6 Terra | Gemini 3.8 Flash | Cheaper |
|---|---|---|---|
| Support reply3,000 in, 400 out. | $10.80 | $3.75 | Gemini 3.8 Flash, 65% less |
| Document summary25,000 in, 1,000 out. | $62.00 | $22.50 | Gemini 3.8 Flash, 64% less |
| Agent task80,000 in (70,000 cached), 3,000 out. | $70.00 | $24.00 | Gemini 3.8 Flash, 66% less |
The token counts are ours, chosen to look like real work; the prices are the makers’. A model with no published cache price bills the agent task’s repeated context at its full input rate.
The small print
What each base rate leaves out, from the makers’ own pages: surcharges, discounts, promotions and cache pricing.
- GPT-5.6 Terra
- OpenAI calls it the mini tier of the 5.6 family; tiered mid here on price. Price cut 20% on 2026-07-30. Requests above 272K input tokens bill 2x input and 1.5x output ($4 / $18). Cache write $2.50. Batch and Flex 50% off. Data residency adds 10%. OpenAI’s pricing page
- Gemini 3.8 Flash
- Launch price through 2026-12-31; from 2027-01-01 it becomes $1.50 / $7.50, cached $0.15. Batch and Flex 50% off; Priority $1.35 / $6.75. Cache storage $0.50 per MTok per hour (rising to $1.00). Google’s pricing page
Other comparisons
Every head to head on the list that involves GPT-5.6 Terra or Gemini 3.8 Flash.
Compare GPT-5.6 Terra and Gemini 3.8 Flash with 52 other models
The price list sets every model’s input and output price side by side, with what a support reply, a document summary and an agent task cost on each.
Prices checked 12 November 2026