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DeepSeek V4.1 Flash vs GPT-6 Luna: API Cost Comparison

Two of the lowest-priced APIs available. DeepSeek is open-weight with automatic prefix caching; Luna has a batch tier.

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  • Updated 7 Nov 2026
DeepSeek V4.1 Flash and GPT-6 Luna pricing side by side
Side by sideDeepSeek V4.1 Flash
DeepSeek
GPT-6 Luna
OpenAI
Input / 1M$0.30$0.10
Output / 1M$1.20$0.50
Cached input / 1M$0.006$0.01
Batch discountNone50% off
Context windowNot published1.05M tokens
Long-prompt surchargeNoneAbove 272K input
TierSmall / fastSmall / fast

Workload

tok
tok
%

Repeated system prompt or docs

%

Jobs that can wait hours

Models

Anthropic
OpenAI
Google
Mistral
DeepSeek

$ per 1M tokens, input / output

Monthly cost · 30 days

Cheapest
$105
GPT-6 Luna
Priciest
$288
DeepSeek V4.1 Flash
Spread
2.7×
priciest vs cheapest
Per 1K users / mo
GPT-6 LunaCheapest
$105$52.50
DeepSeek V4.1 Flash
$288$144
Per 1K users assumesrequests per user per day.

Where the money is

If 60% of your traffic is simple enough for GPT-6 Luna, routing it there instead of DeepSeek V4.1 Flash saves about $110/month.

Caching half your input on DeepSeek V4.1 Flash (a shared system prompt or document) would cut about $88.20/month.

You're looking at $105–$288/month.

Most AI products I audit can cut that 30–60% with routing, caching and shorter prompts.

Get a cost-cutting audit
01

Cost at three traffic levels

Same request on both: 2,000 input tokens and 300 output tokens, no caching, no batch, 30-day month.

Monthly cost of DeepSeek V4.1 Flash vs GPT-6 Luna
Requests / dayDeepSeek V4.1 FlashGPT-6 LunaDifference
1,000$28.80$10.50$18.30
10,000$288$105$183
100,000$2,880$1,050$1,830

By request type:

Cost per 1,000 calls by request type, DeepSeek V4.1 Flash vs GPT-6 Luna
Per 1K callsDeepSeek V4.1 FlashGPT-6 Luna
Classification or routing call$0.1320$0.0450
Support chat reply$0.7500$0.2750
RAG answer over your docs$2.28$0.8000
Long document summary$13.20$4.50
02

When to pick which

  • GPT-6 Luna is 3.0× cheaper on input tokens, which matters most for RAG and long prompts.
  • GPT-6 Luna is 2.4× cheaper on output tokens, which matters most for long answers, code generation and reasoning.
  • Cache reads are 1.7× cheaper on DeepSeek V4.1 Flash ($0.006 vs $0.01 per 1M), so it pulls ahead when your prompts share a long fixed prefix.
  • GPT-6 Luna offers a 50% batch discount for jobs that can wait; DeepSeek V4.1 Flash has no batch tier.
  • DeepSeek V4.1 Flash is open-weight, so you can move to self-hosting later without changing models.
  • GPT-6 Luna bills the whole request at a higher rate once input passes 272,000 tokens.

DeepSeek V4.1 Flash: Very cheap open-weight model with near-free cache hits. Good for repetitive prompts with a shared prefix.

GPT-6 Luna: OpenAI's cheapest current model. Bulk tagging, extraction, routing and lightweight chat.

03

Verdict

GPT-6 Luna wins on price

2.7× cheaper

On price alone, GPT-6 Luna wins: about 2.7× cheaper than DeepSeek V4.1 Flash for a typical request. Price is one input. Run both on 50 of your real prompts, compare the answers and the billed tokens, and route by difficulty if the quality gap only shows up on hard requests.

04

How the math works

Every provider bills input tokens (your prompt, system prompt and retrieved documents) and output tokens (the reply) separately, per million. Output is usually 4–5× the input price, so chatty apps are output-heavy and RAG apps are input-heavy.

cost per request = (fresh_in × input_price
+ cached_in × cached_price
+ out × output_price) / 1,000,000
× (1 − batched_share × batch_discount)
monthly = cost per request × requests per day × 30

Two adjustments are applied automatically. Introductory prices (currently on some Gemini models) are used until their end date. Long-prompt surcharges kick in when your average input crosses the provider's threshold: 272K tokens on current OpenAI models, 100K on Claude Haiku 5.5.

Not modelled: cache-write premiums, priority or fast tiers, regional surcharges, image and audio tokens, and reasoning tokens a model spends before answering (they bill as output, so add them to your output estimate if you use extended thinking).

05

Questions

Which is cheaper, DeepSeek V4.1 Flash or GPT-6 Luna?
For a typical request of 2,000 input and 300 output tokens, GPT-6 Luna is about 2.7× cheaper: $0.00096 per call on DeepSeek V4.1 Flash vs $0.00035 on GPT-6 Luna. At 10,000 requests a day that is $288 vs $105 a month.
Can I use both DeepSeek V4.1 Flash and GPT-6 Luna?
Yes, and many teams do. Put a thin routing layer in front of both: send the requests that need the stronger or larger-context model to it, and everything else to the cheaper one. Keep prompts provider-neutral so you can move traffic when prices change.
How often do DeepSeek and OpenAI change prices?
Often enough that a comparison older than a few months is suspect. The prices on this page were verified on 7 Nov 2026 from each provider's own documentation, linked in the Sources section.
06

Sources

All prices are list prices from each provider's own documentation, standard tier, in USD, last verified on 7 Nov 2026. Providers change prices often; if a number here disagrees with the source, the source wins.

07

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Fine print

Tools: on the house.
Engineer: by the hour.

Knowing your AI bill was free. Cutting it in half isn't, but I'm cheaper than the overspend.

I'm Himanshu, an AI and full-stack engineer. I build MVPs, AI agents and the growth plumbing around them for early-stage startups.

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