Gemini 3.8 Flash vs GPT-6 Luna: API pricing and agent cost
| Model | Provider | Input $/1M | Output $/1M | Cached $/1M | Per task | Per month |
|---|---|---|---|---|---|---|
| Gemini 3.8 Flash | $0.75 | $3.75 | $0.075 | $0.0262 | $78.75 | |
| GPT-6 Luna | OpenAI | $0.1 | $0.5 | $0.01 | $0.0035 | $10.50 |
For an agent making 5 tool calls per task (3,000 input and 800 output tokens per call) and running 100 tasks a day, GPT-6 Luna is the cheaper option at $10.50 a month, versus $78.75 for Gemini 3.8 Flash (7.5× the cost).
This compares list prices only, not quality. Through Dec 31, 2026; $1.50/$7.50 from Jan 1, 2027 (cached input $0.075 to $0.15). Prompts with more than 272K input tokens are priced at 2x input and cache rates and 1.5x output for the full request (OpenAI model page). Derived long-context rate: $0.20 in / $0.02 cached / $0.75 out.
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