API cost decision in 10 seconds

DeepSeek V4 Flash 0731 (batch) vs GPT-5.6 Luna Pro (batch)

Pick DeepSeek V4 Flash 0731 (batch) for lower cost; pick GPT-5.6 Luna Pro (batch) only if the larger context window matters more.

Page updated: 2026-08-28T20:07:51Z Data confirmed: 2026-08-28T22:07:54Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick DeepSeek V4 Flash 0731 (batch) for lower cost; pick GPT-5.6 Luna Pro (batch) only if the larger context window matters more.

On the standard 1M input plus 500K output workload, DeepSeek V4 Flash 0731 (batch) is estimated at $0.28 vs $0.4 for GPT-5.6 Luna Pro (batch), saving $0.12 (30% lower).

Cost-first pickDeepSeek V4 Flash 0731 (batch)

Context-first pickGPT-5.6 Luna Pro (batch)

Sample savings$0.1230%

10x traffic gap$1.2

GPT-5.6 Luna Pro (batch) has more context, but DeepSeek V4 Flash 0731 (batch) saves $0.12 on the standard workload. At 10x that traffic, the same price gap is about $1.2. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

Cost winner changes by workload shape: input-heavy / RAG favors GPT-5.6 Luna Pro (batch), balanced workload favors DeepSeek V4 Flash 0731 (batch), and output-heavy chatbot favors DeepSeek V4 Flash 0731 (batch).

Workload shape	Token mix	Better pick	DeepSeek V4 Flash 0731 (batch)	GPT-5.6 Luna Pro (batch)
Input-heavy / RAG	5M input + 500K output	GPT-5.6 Luna Pro (batch)	$0.84	$0.8
Balanced workload	1M input + 1M output	DeepSeek V4 Flash 0731 (batch)	$0.42	$0.7
Output-heavy chatbot	1M input + 5M output	DeepSeek V4 Flash 0731 (batch)	$1.54	$3.1

Cheaper input GPT-5.6 Luna Pro (batch) $0.14 vs $0.1 / 1M

GPT-5.6 Luna Pro (batch) is $0.04 cheaper per 1M input tokens (28.6% lower; 1.4x difference).

Cheaper output DeepSeek V4 Flash 0731 (batch) $0.28 vs $0.6 / 1M

DeepSeek V4 Flash 0731 (batch) is $0.32 cheaper per 1M output tokens (53.3% lower; 2.14x difference).

Larger context GPT-5.6 Luna Pro (batch) 1.05M vs 1.05M

GPT-5.6 Luna Pro (batch) has 1.42K more context (1x larger).

Sample workload DeepSeek V4 Flash 0731 (batch) $0.28 vs $0.4

DeepSeek V4 Flash 0731 (batch) is $0.12 cheaper on the standard workload (30% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

DeepSeek V4 Flash 0731 (batch) Calculating… Estimated API cost

GPT-5.6 Luna Pro (batch) 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-5.6 Luna Pro (batch) has the lower input price; DeepSeek V4 Flash 0731 (batch) has the lower output price; GPT-5.6 Luna Pro (batch) offers the larger context window. For the 1M input plus 500K output sample, DeepSeek V4 Flash 0731 (batch) is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0.28 for DeepSeek V4 Flash 0731 (batch) and $0.4 for GPT-5.6 Luna Pro (batch).

Best Fit

Choose DeepSeek V4 Flash 0731 (batch) when you care most about lower output-token price.

Choose GPT-5.6 Luna Pro (batch) when you care most about lower input-token price, and larger context window.

Decision Notes

On the standard 1M input plus 500K output workload, DeepSeek V4 Flash 0731 (batch) is estimated at $0.28 vs $0.4 for GPT-5.6 Luna Pro (batch), saving $0.12 (30% lower).
DeepSeek V4 Flash 0731 (batch) is $0.12 cheaper on the standard workload (30% lower).
GPT-5.6 Luna Pro (batch) is $0.04 cheaper per 1M input tokens (28.6% lower; 1.4x difference).
DeepSeek V4 Flash 0731 (batch) is $0.32 cheaper per 1M output tokens (53.3% lower; 2.14x difference).
GPT-5.6 Luna Pro (batch) has 1.42K more context (1x larger).

Head-to-Head Specs

Feature	DeepSeek V4 Flash 0731 (batch) (DeepSeek)	GPT-5.6 Luna Pro (batch) (OpenAI)
Input Price prompt tokens per 1M	$0.14	$0.1
Completion Price per 1M tokens	$0.28	$0.6
Sample Workload Cost 1M input + 500K output	$0.28	$0.4
Context Window	1.05M	1.05M
Release Date	2026-07-31	2026-07-09

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	DeepSeek V4 Flash 0731 (batch)	On the standard 1M input plus 500K output workload, DeepSeek V4 Flash 0731 (batch) is estimated at $0.28 vs $0.4 for GPT-5.6 Luna Pro (batch), saving $0.12 (30% lower).
High-volume input processing	GPT-5.6 Luna Pro (batch)	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	DeepSeek V4 Flash 0731 (batch)	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	GPT-5.6 Luna Pro (batch)	A larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps

DeepSeek V4 Flash (free) can replace DeepSeek V4 Flash 0731 (batch) when lower sample workload cost matters most: $0.
DeepSeek V4 Flash 0731 can replace DeepSeek V4 Flash 0731 (batch) when lower sample workload cost matters most: $0.1.
DeepSeek V4 Flash 0423 can replace DeepSeek V4 Flash 0731 (batch) when lower sample workload cost matters most: $0.17.
gpt-oss-120b (free) can replace GPT-5.6 Luna Pro (batch) when lower sample workload cost matters most: $0.

Larger context near this budget

DeepSeek V4 Flash 0731 offers 1.31M context with $0.1 sample workload cost.
GLM 5.3 Flash offers 1.31M context with $0.2 sample workload cost.
DeepSeek V4 Flash Latest offers 1.31M context with $0.08 sample workload cost.
Llama 4 Scout offers 1.31M context with $0.28 sample workload cost.

Popular competitors

DeepSeek V4 Flash 0731 · DeepSeek · #1
MiMo-V2.5 · Xiaomi · #2
Hy3 · Tencent · #3
Nemotron 3 Ultra (free) · NVIDIA · #4

Cheaper alternatives

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Provider catalogs

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DeepSeek catalog

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OpenAI catalog

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DeepSeek V4 Flash 0731 (batch)

DeepSeek V4 Flash 0731 is a sparse mixture-of-experts model from DeepSeek, with 13B active parameters out of 284B total. This re-post-trained revision is suited for coding, reasoning, and agent workflows....

GPT-5.6 Luna Pro (batch)

GPT-5.6 Luna Pro is the same underlying model as [GPT-5.6 Luna](https://openrouter.ai/openai/gpt-5.6-luna), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. Learn more in OpenAI's docs: https://developers.openai.com/api/docs/guides/reasoning#reasoning-mode