Claude Sonnet 5.5 → DeepSeek V4.1 Flash: cost and quality on real tasks
On the six tasks below, DeepSeek V4.1 Flash from DeepSeek costs 85–87% less than Claude Sonnet 5.5 per request at list prices.
Price per million tokens
Standard list prices, checked 2026-11-12. Prices change often, so check the source before you rely on them.
| Model | Input | Cached input | Output | Source |
|---|---|---|---|---|
| Claude Sonnet 5.5 (current)anthropic/claude-sonnet-5.5 | $2.00 | $0.10 | $10.00 | Anthropic's pricing page |
| DeepSeek V4.1 Flash (new)deepseek/deepseek-v4.1-flash-1017 | $0.30 | $0.006 | $1.20 | DeepSeek's pricing page |
- Note on Claude Sonnet 5.5: Cache hits priced at 0.05x input. Cache writes: 5m $2.50, 1h $4. Batch 50% off.
- Note on DeepSeek V4.1 Flash: Peak-hour price (Mon-Fri 01:00-04:00 and 06:00-10:00 UTC). Off-peak is half: $0.15 in / $0.003 cached / $0.60 out. API model name deepseek-flash = DeepSeek-V4.1-Flash-1017. OpenRouter headline $0.15/$0.60 matches the off-peak rate.
Cost per 1,000 results on six common tasks
What 1,000 requests cost at list price, for six task shapes from different kinds of app. The token counts are illustrative, not measured: your prompts may be longer or shorter, and the switch test below shows your real ones.
| Task, and what goes in and out | Tokens in / out | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Change | Break-even: DeepSeek V4.1 Flash costs no more per result that works if it works first time at least |
|---|---|---|---|---|---|
| Support bot answerInstructions, three help-centre passages and the customer's question in; a short answer out. | 3,000 / 300 | $9.00 | $1.26 | 86% less | 14% as often as Claude Sonnet 5.5 |
| Invoice field extractionInstructions and one invoice's text in; about 15 fields as JSON out. | 2,500 / 250 | $7.50 | $1.05 | 86% less | 14% as often as Claude Sonnet 5.5 |
| Lead scoringScoring rules and one lead's form answers in; a score and a one-line reason out. | 1,200 / 100 | $3.40 | $0.48 | 86% less | 15% as often as Claude Sonnet 5.5 |
| Email reply draftInstructions and the email thread so far in; a reply of about 300 words out. | 1,500 / 400 | $7.00 | $0.93 | 87% less | 14% as often as Claude Sonnet 5.5 |
| TranslationInstructions and about 500 words of text in; the same text in another language out. | 900 / 800 | $9.80 | $1.23 | 87% less | 13% as often as Claude Sonnet 5.5 |
| Search re-rankingA search query and 20 result snippets in; the ids of the best five, in order, out. | 4,000 / 50 | $8.50 | $1.26 | 85% less | 15% as often as Claude Sonnet 5.5 |
Real cost per result: when a switch really saves
Real cost per result is what you actually pay for each result that worked, counting the failed tries. A result that fails gets tried again, and you pay for both tries.
So the price per request is only half the answer. DeepSeek V4.1 Flash stays cheaper per result that works as long as it works first time at least 13% as often as Claude Sonnet 5.5 on translation, and 15% as often on search re-ranking. That's the new cost divided by the current cost, shown for each task in the last column above.
With a gap this big, cost per result rarely decides the switch. What decides it is whether your users notice: answers that fail first time cost you trust and paying customers, not just tokens.
Example, with a made-up rate
Say 8 in 10 of Claude Sonnet 5.5's support bot answers work first time. You pay $9.00 for 1,000 tries and get 800 that work, a real cost of $11.25 per 1,000 support bot answers that work. DeepSeek V4.1 Flash costs $1.26 for 1,000 tries, so it matches that real cost if 12% of its support bot answers work first time, and costs less if more do.
Quality: test it on your own requests
This page can't tell you whether DeepSeek V4.1 Flash handles your requests as well as Claude Sonnet 5.5, and we don't publish quality scores. Quality depends on your prompts and your inputs: a model that answers short English questions well can still fail on long invoices, odd layouts or other languages.
The free model switch test runs your prompt and up to 20 of your real inputs on both models with your own key, through each provider's own API or OpenRouter. You see the answers side by side with the tokens and cost of each, and mark which ones worked.
Test both models on your promptsWhat to compare
- Format: does JSON still parse with the same field names, for extraction and scoring?
- Length and tone: are support answers and email drafts as short and polite as before?
- Refusals: does DeepSeek V4.1 Flash decline requests that Claude Sonnet 5.5 handled?
- Hard inputs: long documents, other languages and messy formatting, not just the easy cases.
- Token counts: Anthropic and DeepSeek count tokens differently, so the same request can cost more or less than the table says. The test shows the real counts.
Questions
Is DeepSeek V4.1 Flash cheaper than Claude Sonnet 5.5?
Per request, yes: it costs 85–87% less on six common tasks. Claude Sonnet 5.5 lists at $2.00 per million input tokens and $10.00 per million output tokens; DeepSeek V4.1 Flash lists at $0.30 and $1.20 (Claude Sonnet 5.5: price checked 12 nov 2026; unchanged since we started tracking it; DeepSeek V4.1 Flash: price checked 12 nov 2026; unchanged since we started tracking it). Per result that works, it depends on how often each model works first time on your inputs: DeepSeek V4.1 Flash stays cheaper per result that works as long as it works first time at least 13% as often as Claude Sonnet 5.5 on translation, and 15% as often on search re-ranking.
How do I work out the break-even for my own app?
Divide what a request costs on DeepSeek V4.1 Flash by what it costs on Claude Sonnet 5.5, using your real token counts. DeepSeek V4.1 Flash is cheaper per result that works as long as its share of results that work first time, divided by Claude Sonnet 5.5's, is above that number. The model switch test gives you the token counts and cost of each request on both models.
Will DeepSeek V4.1 Flash work as well as Claude Sonnet 5.5 for my app?
Nobody can tell you that from a price table or a general benchmark, because it depends on your prompts and inputs. Run 10 to 20 of your real requests through both models with the free model switch test, using your own provider key, and compare the answers side by side before you switch any users.