# Gemini 4 Argon vs GPT-6 Luna

GPT-6 Luna is the cheaper of the 2: for the same tokens, 3 read for each 1 written, Gemini 4 Argon costs 20 times as much. Below are both price lists, what 8 everyday jobs cost a month on each, and how many tokens the same text takes on each, which can change the answer.

- Page, with a calculator for your own job: https://tecyfy.com/prices/compare/gemini-4-argon-vs-gpt-6-luna
- Makers: Gemini 4 Argon from Google, GPT-6 Luna from OpenAI

## Price per million tokens, in US dollars

| | Gemini 4 Argon | GPT-6 Luna |
| --- | --: | --: |
| Input | $2 | $0.10 |
| Cached input | $0.10 | $0.01 |
| Cache write | not listed | $0.125 |
| Output | $10 | $0.50 |
| Blend, 3 read for each 1 written | $4 | $0.20 |
| Batch input | not listed | $0.05 |
| Batch output | not listed | $0.25 |
| Long prompt input (above 272K on GPT-6 Luna) | $2 | $0.20 |
| Long prompt output | $10 | $0.75 |
| Context window, tokens | not listed | 1.05M |
| Capability score (Epoch Capabilities Index; GPT-5 is 150) | 165 | 156 |
| Longest answer, tokens | not listed | 128K |

Gemini 4 Argon: Until 30 November 2026. From 1 December 2026 it is $4 in, $20 out and $0.20 cached.

## The same text, counted by each maker

Our lesson "How AI writes" (https://tecyfy.com/learn/how-ai-works/how-ai-writes), about 1,700 words of English:

- Gemini 4 Argon: about 2,200 tokens. Google does not publish the Gemini tokenizer. Its rule is that a token is about 4 characters, so the count is the characters divided by 4.
- GPT-6 Luna: about 2,100 tokens. GPT-5.6 is counted with o200k_base, the tokenizer OpenAI publishes for it, so its count is exact. OpenAI has not published the tokenizer of GPT-6, so its count is the same o200k_base figure, marked as about.

## What 8 everyday jobs cost a month on each

Each job at its usual runs a day, for 30 days, at the standard price.

| Job | Tokens in, out, runs a day | Gemini 4 Argon | GPT-6 Luna |
| --- | --- | --: | --: |
| A chat question | 300, 500, 100 | $16.80 | 84 cents |
| A hard question, with thinking | 300, 1,400, 100 | $43.80 | $2.19 |
| A long report, summarised | 60,000, 2,000, 20 | $84.00 | $4.20 |
| A 40-turn agent task | 2,800,000, 40,000, 10 | $364 | $21.96 |
| A support bot's reply | 4,000, 300, 2,000 | $432 | $22.20 |
| Sort a message into a category | 250, 5, 50,000 | $825 | $41.25 |
| Read an invoice into fields | 1,500, 250, 1,000 | $165 | $8.25 |
| Review a pull request | 25,000, 4,500, 50 | $143 | $7.13 |

## Questions

### Which is cheaper, Gemini 4 Argon or GPT-6 Luna?

GPT-6 Luna is cheaper: $0.10 per million tokens read and $0.50 per million written, against $2 and $10 on Gemini 4 Argon. On a mix of 3 tokens read for each 1 written, Gemini 4 Argon costs 20 times as much.

### Which is better, Gemini 4 Argon or GPT-6 Luna?

On the Epoch Capabilities Index, an independent score from Epoch AI that combines over 50 benchmarks, Gemini 4 Argon scores 165 and GPT-6 Luna 156, above the top of the range of doubt around GPT-6 Luna's score (GPT-5 is 150). One score is an average; test both on your own work before you switch.

### What does a support bot cost a month on Gemini 4 Argon and GPT-6 Luna?

At 2,000 replies a day, each reading 4,000 tokens (50 percent of them from cache) and writing 300, it costs $432 a month on Gemini 4 Argon and $22.20 on GPT-6 Luna: Gemini 4 Argon costs 19 times as much for this job.

### What does an AI agent task cost on Gemini 4 Argon and GPT-6 Luna?

One 40-turn task that reads 2,800,000 tokens in all, 90 percent of them from cache, and writes 40,000, costs $1.21 on Gemini 4 Argon and 7.3 cents on GPT-6 Luna. At 10 tasks a day that is $364 and $21.96 a month.

### Does the same text take the same number of tokens on Gemini 4 Argon and GPT-6 Luna?

No. Our lesson "How AI writes", 1,700 words long, is about 2,200 tokens on Gemini 4 Argon and about 2,100 on GPT-6 Luna. Each maker cuts text its own way, and every extra token is paid for at the model's price.

### Can I pay less on Gemini 4 Argon and GPT-6 Luna for work that can wait?

On GPT-6 Luna only: with a batch, where you collect the answers later, it costs $0.05 per million tokens read and $0.25 written. Google's price page lists no batch price for Gemini 4 Argon.

## Sources

- [Google: API prices](https://ai.google.dev/gemini-api/docs/pricing)
- [OpenAI: API prices](https://developers.openai.com/api/docs/pricing)
- [Epoch Capabilities Index, by Epoch AI (CC BY 4.0)](https://epoch.ai/benchmarks/eci)

## Other comparisons

- [GPT-6 Luna vs GPT-6 Sol](https://tecyfy.com/prices/compare/gpt-6-luna-vs-gpt-6-sol.md)
- [GPT-5.6 Sol vs GPT-6 Luna](https://tecyfy.com/prices/compare/gpt-5-6-sol-vs-gpt-6-luna.md)
- [GPT-5.6 Terra vs GPT-6 Luna](https://tecyfy.com/prices/compare/gpt-5-6-terra-vs-gpt-6-luna.md)
- [GPT-5.6 Luna vs GPT-6 Luna](https://tecyfy.com/prices/compare/gpt-5-6-luna-vs-gpt-6-luna.md)
- [GPT-5.5 vs GPT-6 Luna](https://tecyfy.com/prices/compare/gpt-5-5-vs-gpt-6-luna.md)
- [GPT-5.5 pro vs GPT-6 Luna](https://tecyfy.com/prices/compare/gpt-5-5-pro-vs-gpt-6-luna.md)