Compare verified published API prices for Gemini 3.8 Flash and GPT-6 Luna. This page compares price, not output quality.
Verified Oct 21, 2026, Gemini 3.8 Flash lists input at $0.75 and output at $3.75 per 1M tokens, while GPT-6 Luna lists $0.10 input and $0.50 output. GPT-6 Luna is 86.7% cheaper on input. GPT-6 Luna is 86.7% cheaper on output. This is a comparison of published prices only, not output quality.
| Model | Input $/1M | Cached input $/1M | Output $/1M | Source | Last verified |
|---|---|---|---|---|---|
| Gemini 3.8 Flash | $0.75 | $0.075 | $3.75 | Official source | Oct 9, 2026 |
| GPT-6 Luna | $0.10 | $0.01 | $0.50 | Official source | Oct 21, 2026 |
Prices from official provider pages, verified on the date shown.
Published rates
| Field | Gemini 3.8 Flash | GPT-6 Luna |
|---|---|---|
| Provider | OpenAI | |
| Input / 1M | $0.75 | $0.10 |
| Cached input / 1M | $0.075 | $0.01 |
| Output / 1M | $3.75 | $0.50 |
| Batch input / 1M | $0.375 | $0.05 |
| Batch output / 1M | $1.875 | $0.25 |
| Context window | 1,048,576 | 1050K |
| Release date | Sep 2, 2026 | Sep 22, 2026 |
| Official source | Google pricing ↗ | OpenAI pricing ↗ |
Standard token prices
Costs below allocate 1M total tokens across each input:output ratio. They use standard prices only, without cache or Batch discounts.
| Input:output ratio | Gemini 3.8 Flash | GPT-6 Luna | Cheaper published price |
|---|---|---|---|
| 10:1 (RAG / long context) | $1.02 | $0.136 | GPT-6 Luna by 86.7% |
| 3:1 (chat) | $1.50 | $0.20 | GPT-6 Luna by 86.7% |
| 1:1 | $2.25 | $0.30 | GPT-6 Luna by 86.7% |
| 1:3 (long generation) | $3.00 | $0.40 | GPT-6 Luna by 86.7% |
Computed examples
| Workload | Assumed volume | Gemini 3.8 Flash | GPT-6 Luna | Difference |
|---|---|---|---|---|
| Side project | 10,000 requests/month | $17.25 | $2.30 | GPT-6 Luna by $14.95 (86.7%) |
| Customer support chatbot | 10,000 conversations/month | $131.74 | $17.57 | GPT-6 Luna by $114.17 (86.7%) |
| Agent task | 1,000 tasks/month | $21.00 | $2.80 | GPT-6 Luna by $18.20 (86.7%) |
Provider conditions
Batch API: input $0.375 and output $1.875 per 1M tokens.
Official pricing notes: Generally available since 2026-09-02. Current pricing applies through 2026-12-31; Standard input/output becomes $1.50/$7.50 per 1M tokens on 2027-01-01.
| Tier | Input | Cached input | Output |
|---|---|---|---|
| Long context | $0.20 | $0.02 | $0.75 |
| Short context | $0.10 | $0.01 | $0.50 |
Batch API: input $0.05 and output $0.25 per 1M tokens.
Verified changes
On Sep 22, 2026, OpenAI replaced GPT-5.6 Luna with GPT-6 Luna: input $0.20 → $0.10 (−50%) and output $1.20 → $0.50 (−58.3%) per 1M tokens.
View this update in the price monitorOperational costs
Retries, failed calls, fallback requests, and longer outputs can raise the cost of completing a task even when the published token price is lower. Model the effect with the LLM Retry & Fallback Cost Calculator, read the cost-per-successful-task guide, or estimate a migration with the Model Switch Cost Calculator.
Primary evidence and next steps
Common questions
GPT-6 Luna is 86.7% cheaper on input. GPT-6 Luna is 86.7% cheaper on output. This compares published list prices, not output quality.
At 800 input and 300 output tokens per request, Gemini 3.8 Flash costs about $17.25 and GPT-6 Luna costs about $2.30 at standard list prices.
At a 10:1 input-to-output token ratio, Gemini 3.8 Flash costs $1.02 and GPT-6 Luna costs $0.136 per 1M total tokens. GPT-6 Luna by 86.7%.
The prices come from Google and OpenAI official pricing sources, verified on Oct 9, 2026 and Oct 21, 2026, respectively. See the AI API pricing dataset.