API cost decision in 10 seconds

GPT-5.5 Pro vs 🔥DeepSeek V4 Flash

Pick DeepSeek V4 Flash for lower cost; pick GPT-5.5 Pro 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 DeepSeek V4 Flash for lower cost; pick GPT-5.5 Pro only if the larger context window matters more.

On the standard 1M input plus 500K output workload, DeepSeek V4 Flash is estimated at $0.2 vs $120 for GPT-5.5 Pro, saving $119.8 (99.8% lower).

Cost-first pickDeepSeek V4 Flash
Context-first pickGPT-5.5 Pro
Sample savings$119.899.8%
10x traffic gap$1198

GPT-5.5 Pro has more context, but DeepSeek V4 Flash saves $119.8 on the standard workload. At 10x that traffic, the same price gap is about $1198. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

DeepSeek V4 Flash stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shapeToken mixBetter pickGPT-5.5 ProDeepSeek V4 Flash
Input-heavy / RAG 5M input + 500K output DeepSeek V4 Flash $240 $0.6
Balanced workload 1M input + 1M output DeepSeek V4 Flash $210 $0.3
Output-heavy chatbot 1M input + 5M output DeepSeek V4 Flash $930 $1.1
Cheaper inputDeepSeek V4 Flash$30 vs $0.1 / 1M
Cheaper outputDeepSeek V4 Flash$180 vs $0.2 / 1M
Larger contextGPT-5.5 Pro1.05M vs 1.05M
Sample workloadDeepSeek V4 Flash$120 vs $0.2

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.
GPT-5.5 ProCalculating…Estimated API cost
DeepSeek V4 FlashCalculating…Estimated API cost
Cheaper for this workloadCalculating…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

DeepSeek V4 Flash has the lower input price, DeepSeek V4 Flash has the lower output price, and GPT-5.5 Pro offers the larger context window.

For a 1M input token plus 500K output token workload, the estimated API cost is $120 for GPT-5.5 Pro and $0.2 for DeepSeek V4 Flash.

Best Fit

Choose GPT-5.5 Pro when you care most about larger context window.

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

Head-to-Head Specs
FeatureGPT-5.5 Pro
(OpenAI)		🔥DeepSeek V4 Flash
(DeepSeek)
Input Price
prompt tokens per 1M		$30$0.1
Completion Price
per 1M tokens		$180$0.2
Sample Workload Cost
1M input + 500K output		$120$0.2
Context Window1.05M1.05M
Release Date2026-04-242026-04-24
Popularity#1
GPT-5.5 Pro

GPT-5.5 Pro is OpenAI’s high-capability model optimized for deep reasoning and accuracy on complex, high-stakes workloads. It features a 1M+ token context window (922K input, 128K output) with support for...

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...

Use-Case Decision Matrix

Use caseBetter pickWhy
Budget-constrained productionDeepSeek V4 FlashOn the standard 1M input plus 500K output workload, DeepSeek V4 Flash is estimated at $0.2 vs $120 for GPT-5.5 Pro, saving $119.8 (99.8% lower).
High-volume input processingDeepSeek V4 FlashLower prompt-token price matters most when prompts or retrieved passages dominate the bill.
Long responses and chatbotsDeepSeek V4 FlashLower output-token price matters most when assistants generate many completion tokens.
RAG or long-document workGPT-5.5 ProA larger context window leaves more room for retrieved passages and source files.