Is Gemini 3.8 Flash more expensive than GPT-6 Luna?

Yes. Gemini 3.8 Flash costs $0.75 per million input tokens and $3.75 per million output tokens, compared to GPT-6 Luna's $0.10 and $0.50 — meaning Luna is about 7.5 times cheaper per token across the board at current list prices.

Will Gemini 3.8 Flash's pricing change soon?

Yes. Gemini 3.8 Flash's current rate is an introductory price that providers indicate will increase after December 31, 2026, roughly doubling to around $1.50/$7.50 per million tokens, which would widen the gap with Luna even further.

Which model has the bigger context window?

They're nearly identical. GPT-6 Luna supports about 1,050,000 tokens and Gemini 3.8 Flash supports about 1,048,576 tokens, so context length isn't a meaningful differentiator between the two — pricing is the real decision point.

Which model is cheaper for output-heavy workloads?

GPT-6 Luna is substantially cheaper for output-heavy workloads. Its output price of $0.50 per million tokens versus Gemini 3.8 Flash's $3.75 per million means generation-heavy tasks like long-form writing or code output cost 7.5x less on Luna.

HEAD-TO-HEAD · BUDGET-TIER · VERIFIED OCTOBER 07, 2026

Gemini 3.8 Flash vs GPT-6 Luna — which is actually cheaper?

Gemini 3.8 Flash and GPT-6 Luna both target high-volume, cost-sensitive workloads, but their list prices sit far apart. Gemini charges $0.75/M input and $3.75/M output, while Luna charges just $0.10/M input and $0.50/M output — a gap worth quantifying before you commit to either.

Spec	Gemini 3.8 Flash	GPT-6 Luna
Input / 1M tokens	$0.75	$0.10
Output / 1M tokens	$3.75	$0.50
Context window	1M	1.05M

The output price gap

The widest gap between these two models is on output tokens, which is exactly where heavy-generation workloads accumulate cost fastest. Gemini 3.8 Flash bills output at $3.75/M versus Luna's $0.50/M, a 7.5x multiple that matches the input-side gap. For any workload that's output-heavy — long completions, code generation, or verbose agent responses — that ratio means Luna's cost advantage compounds rather than shrinks as usage grows.

Context window

Context windows are close enough that they shouldn't be the deciding factor: Gemini 3.8 Flash supports roughly 1,048,576 tokens, while GPT-6 Luna supports a slightly larger 1,050,000 tokens. Neither model's long-context ceiling meaningfully changes the economics here — the price-per-token gap dwarfs any difference in window size.

Worked example

At 100M input tokens and 30M output tokens in a month: Gemini 3.8 Flash costs (100 x $0.75) + (30 x $3.75) = $75.00 + $112.50 = $187.50. GPT-6 Luna costs (100 x $0.10) + (30 x $0.50) = $10.00 + $15.00 = $25.00. At this volume, Luna comes in roughly $162.50 cheaper per month — about 7.5x less expensive overall, matching the per-token ratio.

Prices from the LLM Price Watch daily tracker, 2026-10-07. Prices change; use the calculator with your own usage for an exact comparison, or see the full price table for every tracked model.