API cost decision in 10 seconds

NewGPT Luna Latest vs Gemini 3.8 Flash

Pick GPT Luna Latest when budget and context both matter.

Page updated: 2026-09-12T10:08:10Z Data confirmed: 2026-09-13T03:08:15Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick GPT Luna Latest when budget and context both matter.

On the standard 1M input plus 500K output workload, GPT Luna Latest is estimated at $0.8 vs $2.62 for Gemini 3.8 Flash, saving $1.82 (69.5% lower).

Cost-first pickGPT Luna Latest

Context-first pickGPT Luna Latest

Sample savings$1.8269.5%

10x traffic gap$18.25

GPT Luna Latest is cheaper on the standard workload and also has the larger context window. At 10x that traffic, the same price gap is about $18.25. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

GPT Luna Latest stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	GPT Luna Latest	Gemini 3.8 Flash
Input-heavy / RAG	5M input + 500K output	GPT Luna Latest	$1.6	$5.62
Balanced workload	1M input + 1M output	GPT Luna Latest	$1.4	$4.5
Output-heavy chatbot	1M input + 5M output	GPT Luna Latest	$6.2	$19.5

Cheaper input GPT Luna Latest $0.2 vs $0.75 / 1M

GPT Luna Latest is $0.55 cheaper per 1M input tokens (73.3% lower; 3.75x difference).

Cheaper output GPT Luna Latest $1.2 vs $3.75 / 1M

GPT Luna Latest is $2.55 cheaper per 1M output tokens (68% lower; 3.12x difference).

Larger context GPT Luna Latest 1.05M vs 1.05M

GPT Luna Latest has 1.42K more context (1x larger).

Sample workload GPT Luna Latest $0.8 vs $2.62

GPT Luna Latest is $1.82 cheaper on the standard workload (69.5% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

GPT Luna Latest Calculating… Estimated API cost

Gemini 3.8 Flash Calculating… Estimated API cost

Cheaper for this workload Calculating… Difference: calculating…

This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.

Quick Decision

Verdict

GPT Luna Latest has the lower input price; GPT Luna Latest has the lower output price; GPT Luna Latest offers the larger context window. For the 1M input plus 500K output sample, GPT Luna Latest is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0.8 for GPT Luna Latest and $2.62 for Gemini 3.8 Flash.

Best Fit

Choose GPT Luna Latest when you care most about lower input-token price, lower output-token price, and larger context window.

Choose Gemini 3.8 Flash when its provider, model quality, latency, or availability is more important than the numeric price/context winner.

Decision Notes

On the standard 1M input plus 500K output workload, GPT Luna Latest is estimated at $0.8 vs $2.62 for Gemini 3.8 Flash, saving $1.82 (69.5% lower).
GPT Luna Latest is $1.82 cheaper on the standard workload (69.5% lower).
GPT Luna Latest is $0.55 cheaper per 1M input tokens (73.3% lower; 3.75x difference).
GPT Luna Latest is $2.55 cheaper per 1M output tokens (68% lower; 3.12x difference).
GPT Luna Latest has 1.42K more context (1x larger).

Head-to-Head Specs

Feature	NewGPT Luna Latest (OpenAI)	Gemini 3.8 Flash (Google)
Input Price prompt tokens per 1M	$0.2	$0.75
Completion Price per 1M tokens	$1.2	$3.75
Sample Workload Cost 1M input + 500K output	$0.8	$2.62
Context Window	1.05M	1.05M
Release Date	2026-09-11	2026-09-02

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	GPT Luna Latest	On the standard 1M input plus 500K output workload, GPT Luna Latest is estimated at $0.8 vs $2.62 for Gemini 3.8 Flash, saving $1.82 (69.5% lower).
High-volume input processing	GPT Luna Latest	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	GPT Luna Latest	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	GPT Luna Latest	A larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps

gpt-oss-120b (free) can replace GPT Luna Latest when lower sample workload cost matters most: $0.
gpt-oss-20b (free) can replace GPT Luna Latest when lower sample workload cost matters most: $0.
gpt-oss-20b can replace GPT Luna Latest when lower sample workload cost matters most: $0.1.
gpt-oss-120b can replace GPT Luna Latest when lower sample workload cost matters most: $0.12.

Larger context near this budget

Grok 4.20 Multi-Agent offers 2M context with $2.5 sample workload cost.
Grok 4.20 offers 2M context with $2.5 sample workload cost.
GLM 5.3 Flash offers 1.31M context with $0.4 sample workload cost.
DeepSeek V4 Flash 0731 offers 1.31M context with $0.08 sample workload cost.

Popular competitors

Hy4 preview · Tencent · #1
GPT-5.6 Luna · OpenAI · #2
GLM 5.3 Flash · Z.ai · #3
DeepSeek V4 Flash 0731 · DeepSeek · #4

Cheaper alternatives

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Larger context alternatives

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Provider catalogs

Compare models within provider hubs before choosing a final API vendor.

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OpenAI catalog

Review all tracked OpenAI models before deciding whether this matchup is the right shortlist.

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Google catalog

Check other Google models with comparable pricing, context, or release timing.

Open Google models

GPT Luna Latest

This model always redirects to the latest model in the GPT Luna family.

Gemini 3.8 Flash

Gemini 3.8 Flash is Google's most intelligent Flash model with significant gains from 3.7 Flash across software engineering, agentic tasks, and multi-step reasoning.