API cost decision in 10 seconds

🔥DeepSeek V4 Flash vs 🔥Step 3.5 Flash

Pick Step 3.5 Flash for lower cost; pick DeepSeek V4 Flash only if the larger context window matters more.

Pricing data updated:  Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Step 3.5 Flash for lower cost; pick DeepSeek V4 Flash only if the larger context window matters more.

On the standard 1M input plus 500K output workload, Step 3.5 Flash is estimated at $0.25 vs $0.25 for DeepSeek V4 Flash, saving $0.002 (0.8% lower).

Cost-first pickStep 3.5 Flash
Context-first pickDeepSeek V4 Flash
Sample savings$0.0020.8%
10x traffic gap$0.02

DeepSeek V4 Flash has more context, but Step 3.5 Flash saves $0.002 on the standard workload. At 10x that traffic, the same price gap is about $0.02. Use the calculator below to replace the sample workload with your own token volume.

Cheaper input Step 3.5 Flash $0.126 vs $0.1 / 1M

Step 3.5 Flash is $0.03 cheaper per 1M input tokens (20.6% lower; 1.26x difference).

Cheaper output DeepSeek V4 Flash $0.252 vs $0.3 / 1M

DeepSeek V4 Flash is $0.05 cheaper per 1M output tokens (16% lower; 1.19x difference).

Larger context DeepSeek V4 Flash 1.05M vs 262.14K

DeepSeek V4 Flash has 786.43K more context (4x larger).

Sample workload Step 3.5 Flash $0.25 vs $0.25

Step 3.5 Flash is $0.002 cheaper on the standard workload (0.8% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.
DeepSeek V4 Flash Calculating… Estimated API cost
Step 3.5 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

Step 3.5 Flash has the lower input price; DeepSeek V4 Flash has the lower output price; DeepSeek V4 Flash offers the larger context window. For the 1M input plus 500K output sample, Step 3.5 Flash is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0.25 for DeepSeek V4 Flash and $0.25 for Step 3.5 Flash.

Best Fit

Choose DeepSeek V4 Flash when you care most about lower output-token price, and larger context window.

Choose Step 3.5 Flash when you care most about lower input-token price.

Decision Notes
  • On the standard 1M input plus 500K output workload, Step 3.5 Flash is estimated at $0.25 vs $0.25 for DeepSeek V4 Flash, saving $0.002 (0.8% lower).
  • Step 3.5 Flash is $0.002 cheaper on the standard workload (0.8% lower).
  • Step 3.5 Flash is $0.03 cheaper per 1M input tokens (20.6% lower; 1.26x difference).
  • DeepSeek V4 Flash is $0.05 cheaper per 1M output tokens (16% lower; 1.19x difference).
  • DeepSeek V4 Flash has 786.43K more context (4x larger).
Head-to-Head Specs
Feature🔥DeepSeek V4 Flash
(DeepSeek)		🔥Step 3.5 Flash
(StepFun)
Input Price
prompt tokens per 1M		$0.126$0.1
Completion Price
per 1M tokens		$0.252$0.3
Sample Workload Cost
1M input + 500K output		$0.25$0.25
Context Window1.05M262.14K
Release Date2026-04-242026-01-29
Popularity Rank
current rank		#4#15

Use-Case Decision Matrix

Use caseBetter pickWhy
Budget-constrained productionStep 3.5 FlashOn the standard 1M input plus 500K output workload, Step 3.5 Flash is estimated at $0.25 vs $0.25 for DeepSeek V4 Flash, saving $0.002 (0.8% lower).
High-volume input processingStep 3.5 FlashLower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbotsDeepSeek V4 FlashLower output-token price matters most when assistants generate many completion tokens.
RAG or long-document workDeepSeek V4 FlashA larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Cheaper alternatives

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Larger context alternatives

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Provider catalogs

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DeepSeek catalog

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StepFun catalog

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DeepSeek V4 Flash

DeepSeek V4 Flash is an efficiency-optimized Mixture-of-Experts model from DeepSeek with 284B total parameters and 13B activated parameters, supporting a 1M-token context window. It is designed for fast inference and...

Step 3.5 Flash

Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token....