According to Woofun AI, the private capital market showed an extreme K-type differentiation in September: AI giant OpenAI's stock price soared by 32.3%, while collaboration platform Airtable experienced a 56.1% drop.
This sharp divergence in valuation is not an isolated incident; it is a direct reflection of the widening structural rift within the private market. Although the Equal Weighted Private Market Index published by Forge recorded a moderate increase of 1.4% in the same month in an attempt to smooth out individual fluctuations, this macro data conceals a huge gap in the performance of underlying assets. Investor sentiment is shifting from general rise to extreme pickiness, leading to an accelerated concentration of capital at the head, while companies lacking clear acquisition expectations or growth stories are facing severe pressure to revalue their valuations.
In the Forge Accuidity Private Market Index, which is weighted by market capitalization, OpenAI contributed 3.4% of the overall increase as a core weight stock, and became the absolute main force driving the index upward. Meanwhile, the stock price of defense technology company Anduril rose 7.3%, and the stock price of listed company SpaceX (SPCX.US) rose 5%, which together constituted a bright moment for the market.
However, losses in other sectors seriously dragged down the overall performance: Airtable was bought by Bending Spoons (BSP.US) for $1.28 billion, which directly caused its share price to plummet; API development platform Postman shares fell 33.7%, cryptocurrency exchange Kraken shares fell 19.1%, and AI chip startup SambaNova Systems shares fell 12.4%. In stark contrast, Fin, previously known as Intercom, soared 78.7% in stock price after being bought by Salesforce (CRM.US) for $3.6 billion on September 10.
This extreme performance, based on differences in acquisition prices, company development stages, and investor demand, reveals that the private market is undergoing a profound revaluation. According to data compiled by Woofun AI, only 43.5% of the new or updated purchase intentions on the Forge market in September came from buyers. This percentage continued to decline from 45% in August and 48% in July, setting a record for the fourth consecutive month of decline, and buyer participation fell to its lowest level in nearly two years.
The evolution of the transaction structure in the secondary market further confirms the increased bargaining power of buyers. In September, the median price of secondary market transactions was 9% lower than the companies' previous financing valuation, while in August this discount was only 3%. In the high-price trading range, the premium space was also drastically compressed: the 90th percentile transaction price premium plummeted to 15% from 58% in August, and the 75th percentile transaction price premium narrowed from 11% to 6%.
This change shows that as sellers' participation increases, the balance between supply and demand in the market has been reversed, and buyers have more bargaining chips, providing a window for investors seeking opportunities to enter the market at lower prices. However, Forge also pointed out that monthly price changes may only reflect changes in the composition of current trading companies, and do not necessarily represent a systematic adjustment of the overall market price.
Notably, despite pressure from the secondary market, the valuation resilience of large private companies is still remarkable. Of the 40 companies that Forge tracked with a valuation of at least $20 billion, 28 (70%) maintained or raised their valuation levels in recent financings.
This echelon includes Anduril, valued at $123.8 billion by Forge, fintech Ramp, valued at $60 billion, and AI startup Cognition, valued at $48 billion. Since the beginning of August, 5 companies have completed financing at a valuation of $20 billion or more, while only 8 such transactions were recorded throughout 2025, showing that capital's demand for top assets has not weakened as the overall cooling of the market.
Weakness in the private market is not a common phenomenon; on the one hand, companies with strong growth potential and clear exit paths can still attract high capital; on the other hand, companies that lack a unique competitive advantage or have uncertain acquisition prospects face sharp revisions in valuations. For investors, the core challenge is to accurately identify those targets for which early financing valuations are still reasonable, and avoid falling into pricing traps caused by fluctuations in market sentiment. As buyer participation continues to be sluggish and discounts expand in the secondary market, liquidity in the private market may be further concentrated in the future, and the trend of differentiation may continue.