Claude Opus 5 vs DeepSeek-V3 (Legacy API Alias)

Side-by-side technical and economic comparison between Anthropic's Claude Opus 5 and DeepSeek's DeepSeek-V3 (Legacy API Alias).

Verdict: DeepSeek-V3 (Legacy API Alias) is about 98% cheaper than Claude Opus 5 at a typical 3:1 input-to-output mix ($0.175 vs $10.00 per 1M blended tokens). Claude Opus 5 offers the larger context window (1M tokens).

Endpoint Availability & Transition Notice

• DeepSeek-V3 (Legacy API Alias): Classified as a Legacy Reference model (Legacy Reference (API Aliased)).

Claude Opus 5 vs DeepSeek-V3 (Legacy API Alias) Pricing & Specs

Metric	Claude Opus 5	DeepSeek-V3 (Legacy API Alias)	Advantage
Provider Organization	Anthropic	DeepSeek	—
Standard Input / 1M	$5.00	$0.14	DeepSeek-V3 (Legacy API Alias) (97% lower)
Cached Input / 1M	$0.50	$0.014	DeepSeek-V3 (Legacy API Alias) lower
Output / 1M	$25.00	$0.28	DeepSeek-V3 (Legacy API Alias) lower
Context Window	1M	128k	Claude Opus 5 (1M)
Max Generation Tokens	16.4k	8.2k	Claude Opus 5
Tokenizer Family	Anthropic Claude BPE (~65k vocabulary)	DeepSeek Byte-level BPE (~128k vocabulary)	—

Monthly Cost: Claude Opus 5 vs DeepSeek-V3 (Legacy API Alias)

Workload (per month)	Claude Opus 5	DeepSeek-V3 (Legacy API Alias)
Chatbot10k requests · 500 in / 200 out	$75.00	$1.26
RAG app100k requests · 8,000 in / 1,200 out	$7,000.00	$145.60
Coding agent100k requests · 12,000 in / 2,000 out	$11,000.00	$224.00

Standard rates, no caching or batch discounts. Model your own numbers below.

Interactive Side-by-Side Cost Simulator

Live Delta

Input Tokens / Req2,500

Output Tokens / Req800

Daily Requests10,000

Claude Opus 5

$8,062.50 / month

$0.0269 / request

DeepSeek-V3 (Legacy API Alias)LOWER COST

$124.95 / month

$0.00042 / request

Selecting DeepSeek-V3 (Legacy API Alias) saves $7,937.55 / month (98.5% savings) over Claude Opus 5.

When to Choose Claude Opus 5

Opt for Claude Opus 5 when your engineering requirements prioritize Anthropic's ecosystem, specific tokenizer efficiencies (Calibrated Claude Tokenizer (±3%)), or when your expected prompt-to-completion ratios favor its $5/M input rate.

Claude Opus 5 Specs & Documentation

When to Choose DeepSeek-V3 (Legacy API Alias)

Opt for DeepSeek-V3 (Legacy API Alias) when looking for DeepSeek's tooling integration, specific context window depth (128k tokens), or when output generation volume favors its $0.28/M rate.

DeepSeek-V3 (Legacy API Alias) Specs & Documentation

Claude Opus 5 vs DeepSeek-V3 (Legacy API Alias) FAQ

Is Claude Opus 5 cheaper than DeepSeek-V3 (Legacy API Alias)?

At a typical 3:1 input-to-output token mix, DeepSeek-V3 (Legacy API Alias) is about 98% cheaper than Claude Opus 5. Claude Opus 5 costs $5 per 1M input and $25 per 1M output tokens; DeepSeek-V3 (Legacy API Alias) costs $0.14 and $0.28.

Which has a larger context window, Claude Opus 5 or DeepSeek-V3 (Legacy API Alias)?

Claude Opus 5 has the larger context window: 1M tokens vs 128k.

Do Claude Opus 5 and DeepSeek-V3 (Legacy API Alias) support prompt caching?

Claude Opus 5: yes, cached input costs $0.5/1M. DeepSeek-V3 (Legacy API Alias): yes, cached input costs $0.014/1M.