Best Reasoning LLMs on a Budget: o3-mini, DeepSeek R1, Claude Thinking Compared
Compare the most affordable reasoning LLMs in 2026 — OpenAI o3-mini, DeepSeek R1, Claude extended thinking, and Gemini 2.5 Pro thinking — by quality, price, and quality per dollar.
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Frequently Asked Questions
What's the cheapest reasoning LLM in 2026?
DeepSeek R1 at $0.55 input / $2.19 output. Quality score 73, close to flagship reasoning quality at roughly 5% of OpenAI o3's price. Hosted via DeepSeek's API or via OpenRouter for a small markup.
Is o3-mini a real budget option or just labeled that way?
Real budget but watch the output side. At $1.10 input / $4.40 output, list price is moderate — but thinking tokens are billed at output rates and a hard query can easily consume 10,000 thinking tokens. Plan effective cost-per-query at 2–5x the listed output rate.
Should I use Claude extended thinking on Haiku 4.5 to save money?
Claude Haiku 4.5 doesn't support extended thinking — it's a fast-tier model. Thinking is available on Sonnet 4.7 and Opus 4 only. For cheap reasoning in the Anthropic ecosystem, the better path is Sonnet 4.7 without thinking ($3/$15) for moderate problems, then escalate to Opus 4 with thinking for the genuinely hard ones.
How does Gemini 2.5 Pro's 'thinking' compare to o3 and R1?
Gemini 2.5 Pro ships thinking as a native mode rather than a separate tier — same input/output prices ($1.25/$5) but with chain-of-thought enabled. Quality on reasoning benchmarks lags o3 and R1 slightly (76 vs 78–82) but the price advantage is large, making it the best 'cheap general-purpose reasoning' default for many teams.
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