Pricing at a glance
| Metric | DeepSeek V4 Pro | GPT-5.5 |
|---|---|---|
| Provider | DeepSeek | OpenAI |
| Tier | Efficient frontier | Frontier |
| Input / 1M tokens | $0.435 | $5.00 |
| Output / 1M tokens | $0.87 | $30.00 |
| Cached input / 1M | $0.0145 | $2.50 |
| Context window | 1,000,000 tokens | 256,000 tokens |
Cost per 1,000 calls, by workload
Output tokens cost more than input tokens, so the “cheaper” model flips depending on how much your workload reads versus writes. Each row prices 1,000 identical calls:
| Workload | DeepSeek V4 Pro | GPT-5.5 | Cheaper |
|---|---|---|---|
| Short chat turn1K in / 500 out — a typical assistant reply | $0.87 | $20.00 | DeepSeek V4 Pro (−96%) |
| RAG answer8K in / 800 out — retrieved context + grounded answer | $4.18 | $64.00 | DeepSeek V4 Pro (−93%) |
| Long-doc summary50K in / 2K out — summarize a long document | $23.49 | $310.00 | DeepSeek V4 Pro (−92%) |
| Bulk classification2K in / 50 out — label/route at high volume | $0.9135 | $11.50 | DeepSeek V4 Pro (−92%) |
These are list prices for the exact token mix shown. Model your real traffic — your own token counts, prompt-cache hit rate, and monthly volume — in the LLM API Cost Calculator, or see where both land among all 25 models in the 2026 LLM API Pricing Study.
The verdict
On the workloads above, DeepSeek V4 Pro is the cheaper option more often (4 of 4 task shapes), driven mainly by its lower output rate ($0.87 vs $30.00 per 1M output). A simple chat turn at 1,000 calls is $0.87 on DeepSeek V4 Pro versus $20.00 on the other — a 96% difference that compounds at scale.
Don't ignore prompt caching
If your prompts share a large fixed prefix (a system prompt, retrieved docs, few-shot examples), caching changes the math. DeepSeek V4 Pro bills cached input at $0.0145/1M (vs $0.435 fresh), and GPT-5.5 at $2.50/1M (vs $5.00 fresh). For input-heavy, repetitive traffic that can swing the cheaper choice — the calculator lets you set a cache-hit ratio.
Cost is one axis — not the whole decision
This page compares price only. It does not rank quality, latency, tool-use reliability, or rate limits, which differ between DeepSeek V4 Pro and GPT-5.5 and often matter more than a few dollars per thousand calls. Use cost to size the budget, then validate the cheaper model on your own evals before you switch.
FAQ
Is DeepSeek V4 Pro or GPT-5.5 cheaper?
DeepSeek V4 Pro wins on most workloads we model, e.g. $0.87 vs $20.00 per 1,000 short chat turns. Your real answer depends on your input/output ratio — output tokens are the expensive half.
Are these the official prices?
They reflect each provider's published list pricing, verified 2026-05-28, sourced from DeepSeek and OpenAI. Enterprise and committed-use discounts can lower them — always confirm on the provider's pricing page before budgeting.
Pricing verified 2026-05-28. Independent analysis, not affiliated with DeepSeek or OpenAI. Confirm live rates on each provider's official pricing page.