A Chinese Startup Just Undercut OpenAI on Price by a Wide Margin

Chinese AI lab StepFun launched its flagship model on September 20. The StepFun Step 5 Preview is already turning heads for one reason as much as any benchmark: price.

The 600-billion-parameter sparse mixture-of-experts model went live with API pricing of $1.00 per million input tokens. Output runs $2.70 per million tokens. That undercuts several Western frontier labs by a wide margin. It still scores competitively on independent benchmarks.

What the StepFun Step 5 Preview Actually Is

Step 5 Preview carries roughly 600 billion total parameters. About 27 billion activate per token. That sparse architecture keeps inference costs down while preserving capacity. It supports a one-million-token context window. It takes both text and image inputs. The design targets long, complex tasks rather than short chat exchanges.

How It Stacks Up Against the Field

Step 5 scored 44 on the widely tracked Intelligence Index. That matches Kimi K3 Max, another Chinese frontier model. In one benchmark test, it completed a 24-hour autonomous optimization task. It ran at 508 TFlops on H100 GPU cores. StepFun points to that result as evidence the model can sustain long, agentic workloads without human help.

Matching a well-regarded rival like Kimi K3 Max does not by itself prove Step 5 leads the field. But it places StepFun firmly among the top tier of Chinese labs. Those labs now compete directly with the largest Western AI companies on capability, not just cost.

The Pricing Move That Has Rivals Watching

StepFun built the release around long-horizon agent workloads. Think AI coding, software engineering, financial analysis and professional knowledge work. Pairing that focus with aggressive pricing puts direct pressure on Western labs. Enterprise customers running high-volume agentic tasks watch token costs closely. Those costs add up fast at scale.

Open Weights Land October 15

Unlike many frontier releases that stay fully closed, StepFun has committed to opening the model’s weights on October 15, 2026. That gives outside researchers and companies a firm date to plan around. It continues a pattern of Chinese labs using open weights as a lever against closed Western rivals.

Why Chinese Labs Keep Undercutting on Price

StepFun’s pricing move follows a broader pattern among Chinese AI labs this year. Several have used aggressive token pricing to win developer mindshare. That holds even when their raw benchmark scores trail the very top Western models. The strategy leans on a simple bet. Once developers build workflows around a cheaper model, switching costs make it harder for pricier rivals to win them back.

That approach has drawn scrutiny from analysts. They question whether the pricing holds up at scale. For now, though, it has pulled models like Step 5 into serious enterprise evaluations. Those evaluations might otherwise have gone straight to established Western providers.

Where StepFun Fits Among Chinese AI Labs

StepFun is one of several Chinese AI labs that have released a series of models under a numbered naming scheme, steadily scaling parameter counts with each generation. Step 5 Preview is the company’s most ambitious release to date, both in size and in the workloads it targets.

Unlike rivals that lead with chat or search products, StepFun has positioned this release around agentic and enterprise workloads from the start. That focus shapes how the company talks about the model. Its own materials emphasize coding and financial-analysis benchmarks over general conversational ability.

What This Means for Enterprise AI Buyers

Enterprise teams evaluating AI vendors now have another low-cost option to weigh alongside the established players. Procurement teams say token pricing has become a bigger factor in vendor selection as usage scales into the billions of tokens monthly. A cheaper model that performs adequately can save real money at that volume, even if it lags top benchmarks slightly.

Data residency and compliance concerns may still steer some Western enterprise buyers away from Chinese-hosted models, regardless of price. That question is likely to shape how far StepFun’s pricing advantage actually translates into enterprise contracts outside China.

What to Watch Before the Weights Drop

The real test comes once independent developers get hands-on access to the open weights next month. Benchmark scores from a lab’s own team invite scrutiny. The coming weeks will show whether Step 5’s real-world coding and agent performance holds up outside StepFun’s own testing environment.

Until then, the API launch already lets outside developers test the model directly. That should produce a clearer, independent picture of its performance well before the October 15 open-weights date.

Straight Answers on StepFun’s New Model

What is the StepFun Step 5 Preview?

A 600-billion-parameter sparse mixture-of-experts AI model from Chinese lab StepFun, launched September 20, 2026, with about 27 billion parameters active per token.

How much does it cost to use?

API pricing is $1.00 per million input tokens and $2.70 per million output tokens.

What is it designed for?

Long-horizon agent workloads such as AI coding, software engineering, financial analysis and professional knowledge work.

How big is its context window?

One million tokens, with support for both text and image inputs.

When do open weights arrive?

StepFun has scheduled the model’s weights to open on October 15, 2026.

Sources

• MarkTechPost — StepFun launches Step 5 Preview: A 600B-total, 27B-active MoE model with 1M context. https://www.marktechpost.com/2026/09/20/stepfun-launches-step-5-preview/
• Pandaily — StepFun launches Step 5 Preview: 600B sparse MoE, 1M context, weights open Oct 15. https://pandaily.com/stepfun-step-5-preview-600b-moe-1m-context

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