Cost per coding-agent request

Is Gemini 3.8 Flash or GPT-6 Luna cheaper for coding agents?

For coding agents, Gemini 3.8 Flash costs 12x as much as GPT-6 Luna per request ($0.048 vs $0.0041 on our measured traffic), because Gemini 3.8 Flash lists at $1.50 input, $0.15 cached input and $7.50 output per million tokens against $0.10, $0.01 and $0.50 for GPT-6 Luna, and GPT-6 Luna charges more for prompts over 272K tokens.

List prices: Gemini API pricing, OpenAI API pricing, checked 2026-10-13. Request costs: Standard Compute gateway data, 79,301 coding-agent requests from 75 users, Sep 13 to Oct 12, 2026. How we compute this

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Cost per coding-agent request, side by side

Cost at list price	GPT-6 Luna	Gemini 3.8 Flash
Prompt under 100K tokens50% of requests, 87% of input cached	$0.0015	$0.023
Prompt of 100K to 272K39% of requests, 88% of input cached	$0.0039	$0.058
Prompt over 272K tokens11% of requests, 86% of input cached	$0.017	$0.13
Average request	$0.0041	$0.048
100 requests	$0.41	$4.83
Median session16 requests; a session ends after 10 idle minutes	$0.045	$0.65
A month of regular usemedian of 20 users active on 5+ days	$5.83	$73.52

Each logged request priced at the vendor’s list rates for its own token counts, including cache reads and any higher rate for long prompts. Average output: 698 tokens per request.

Benchmarks, speed and latency, side by side

Artificial Analysis	GPT-6 Luna	Gemini 3.8 Flash
Intelligence Index10 evaluations, 0 to 100	38	41
Terminal-Bench 4.0agentic coding in a terminal	12.6%	19.7%
Output speedmedian	136 tokens/s	145 tokens/s
Time to first answer tokenincludes thinking time	101 s	24 s

Source: Artificial Analysis (artificialanalysis.ai). Measured variants: GPT-6 Luna (Max), speed on OpenAI; Gemini 3.8 Flash (High), speed on Google. Fetched October 13, 2026. Artificial Analysis runs Terminal-Bench 4.0 in its own setup, so its scores differ from the tbench.ai leaderboard.

What to watch for

Gemini 3.8 Flash figures use Google's standard price from January 1, 2027; until then Google charges half. GPT-6 Luna scores close to it on the benchmarks above, so the cheaper request is not bought with much lower ability.

FAQ

Is GPT-6 Luna cheaper than Gemini 3.8 Flash for coding agents?

Yes, at list prices. 100 average coding-agent requests cost $0.41 on GPT-6 Luna and $4.83 on Gemini 3.8 Flash. A median 16-request session costs $0.045 vs $0.65. Measured on 79,301 real coding-agent requests (Sep 13 to Oct 12, 2026).

How much does a month of Gemini 3.8 Flash vs GPT-6 Luna cost?

For the median regular user in our data (1,478 requests in 30 days), about $73.52 on Gemini 3.8 Flash and $5.83 on GPT-6 Luna at list price. Heavier users pay proportionally more.

Gemini 3.8 Flash vs GPT-6 Luna: which is better for agents?

Gemini 3.8 Flash scores higher on output quality (7.9/10 vs 7.5/10), while GPT-6 Luna is the cheaper option. Gemini 3.8 Flash is best for high-throughput agents and Gemini CLI users who want speed and big context; GPT-6 Luna is best for cheap, fast subtasks, routing and subagents in OpenAI-based stacks. Live community votes on this page show what people actually prefer.

Can I switch between Gemini 3.8 Flash and GPT-6 Luna in the same agent?

Yes. Model-agnostic agents (Cline, Aider, OpenClaw, Hermes Agent, Kilo Code, OpenCode, Continue) let you swap models per task. Many people route hard tasks to the stronger model and routine work to the cheaper one.