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Gemini 3.5 Flash vs DeepSeek V4 Pro
A straight cost comparison of Gemini 3.5 Flash (Google Gemini) and DeepSeek V4 Pro (DeepSeek), per 1,000,000 tokens, verified October 2026.
Rate-by-rate comparison
| Metric | Gemini 3.5 Flash | DeepSeek V4 Pro | Winner |
|---|---|---|---|
| Input / 1M | $1.50 | $1.32 | DeepSeek V4 Pro |
| Cached input / 1M | $0.15 | $0.044 | DeepSeek V4 Pro |
| Cache write / 1M | — | — | Tie |
| Output / 1M | $9 | $3.96 | DeepSeek V4 Pro |
| Context window | 1,000,000 | 1,000,000 | Tie |
| Batch API | Yes | No | Gemini 3.5 Flash |
| Long-context tier | None | None | — |
For per-token metrics, the lower number wins. For context window and batch support, the higher or broader option wins. A dash means the provider does not publish that rate: a missing cache-write fee means writes are not billed per token, while a missing cached-input rate means cache hits bill at the full input rate.
Blended cost: 1M input + 250K output
| Model | Blended cost | Difference |
|---|---|---|
| Gemini 3.5 Flash | $3.75 | +$1.44 |
| DeepSeek V4 Pro | $2.31 | Cheaper |
Ten workloads, two bills
The same two models, priced across ten workloads that differ only in their input:output ratio. Nothing else changes — no retries, no system prompt, no middleware.
| Workload | Gemini 3.5 Flash | DeepSeek V4 Pro | Winner |
|---|---|---|---|
| Classification 100K reqs · 500 in / 10 out | $84 | $69.96 | DeepSeek V4 Pro |
| Data extraction 10K reqs · 2K in / 200 out | $48 | $34.32 | DeepSeek V4 Pro |
| Support chat 1K reqs · 4K in / 600 out | $11.40 | $7.66 | DeepSeek V4 Pro |
| Code review 2K reqs · 8K in / 1.5K out | $51 | $33 | DeepSeek V4 Pro |
| Summarisation 1K reqs · 20K in / 1K out | $39 | $30.36 | DeepSeek V4 Pro |
| Agent loop 5K reqs · 12K in / 2K out | $180 | $119 | DeepSeek V4 Pro |
| Translation 500 reqs · 15K in / 15K out | $78.75 | $39.60 | DeepSeek V4 Pro |
| Long-document QA 200 reqs · 120K in / 800 out | $37.44 | $32.31 | DeepSeek V4 Pro |
| Cached RAG 1K reqs · 50K in (45K cached) / 1K out | $23.31 | $12.60 | DeepSeek V4 Pro |
| Nightly batch 10K reqs · 10K in / 2K out | $165 | $211 | Gemini 3.5 Flash |
Gemini 3.5 Flash wins 1 of 10, DeepSeek V4 Pro wins 9 of 10. The winner is set by the token mix, not by the headline rate.
Where the two bills cross over
DeepSeek V4 Pro is cheaper on both sides of the mix: $1.32 vs $1.50 per million input tokens, and $3.96 vs $9 per million output. No input:output ratio reverses that, so on price alone the other model never becomes the better choice — it has to win on context, latency or output quality.
Cost at four scales
The same support-chat workload (4K input, 600 output per request) at four monthly volumes.
| Requests / month | Gemini 3.5 Flash | DeepSeek V4 Pro | Difference |
|---|---|---|---|
| 100 | $1.14 | $0.766 | DeepSeek V4 Pro cheaper by $0.374 |
| 1,000 | $11.40 | $7.66 | DeepSeek V4 Pro cheaper by $3.74 |
| 10,000 | $114 | $76.56 | DeepSeek V4 Pro cheaper by $37.44 |
| 100,000 | $1,140 | $766 | DeepSeek V4 Pro cheaper by $374 |
What caching does to each bill
Caching only helps the part of the prompt that repeats. This is the support-chat workload (1,000 requests, 4,000 input tokens each) with an increasing share of that prompt served from a warm cache, written once on the first request.
| Cached share of the prompt | Gemini 3.5 Flash | DeepSeek V4 Pro | Winner |
|---|---|---|---|
| 0% | $11.40 | $7.66 | DeepSeek V4 Pro |
| 50% | $8.70 | $5.11 | DeepSeek V4 Pro |
| 80% | $7.08 | $3.58 | DeepSeek V4 Pro |
| 95% | $6.28 | $2.81 | DeepSeek V4 Pro |
Both models publish a cached-read rate, so the discount is comparable: Gemini 3.5 Flash reads cache at $0.15 per million, DeepSeek V4 Pro at $0.044.
Which one should you pick?
Gemini 3.5 Flash wins on nightly batch, while DeepSeek V4 Pro wins on classification, data extraction, support chat, code review, summarisation, agent loop, translation, long-document qa, cached rag.
Beyond price, the two differ on input rate ($1.50 vs $1.32); output rate ($9 vs $3.96); cached-input rate ($0.15 vs $0.044); batch support (yes vs no).
Batch mode is available on Gemini 3.5 Flash, which halves the nightly job. Both publish cached-input discounts, so a stable system prompt is worth caching on either.
FAQ
Is Gemini 3.5 Flash cheaper than DeepSeek V4 Pro?
On a blended 1M-input-plus-250K-output workload, DeepSeek V4 Pro is cheaper by 38% ($2.31 vs $3.75). The gap changes for cache-heavy prompts and for batch jobs, as the workload table shows.
Which handles longer prompts, Gemini 3.5 Flash or DeepSeek V4 Pro?
Both models share the same 1,000,000-token context window. Neither model publishes a long-context surcharge.
Do both models support prompt caching?
Gemini 3.5 Flash bills cached reads at $0.15 per 1M; DeepSeek V4 Pro at $0.044.
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