Hard drive prices started changing daily
Last August, a former ByteDance employee intended to buy two large-capacity hard drives to store tick-level market data for a quantitative trading platform. After placing the order on Pinduoduo, he noticed that the same Seagate model kept rising in price day after day, rather than fluctuating with promotions. Using price-tracking tools like Manmanmai and Keepa, he pulled historical price curves for multiple large-capacity models from both Seagate and Western Digital. The conclusion was consistent: the entire product line of large mechanical hard drives was experiencing a sustained, one-way price increase. This anomaly signaled a deeper structural cause rather than temporary retail price adjustments.
Tracing the cause: AI is competing for hard drives
Further investigation revealed that while the market focuses on AI's demand for GPUs, the demand for storage is equally massive. Large model training and inference generate enormous data that must be stored long-term at low cost, relying primarily on nearline enterprise hard drives rather than SSDs. Major cloud providers—Microsoft, Amazon, Google, Meta—are aggressively purchasing such drives. Seagate's HAMR technology increases per-drive capacity, perfectly matching data center needs. With enterprise orders offering higher margins, manufacturers prioritize them, squeezing retail supply and pushing up consumer prices. Seagate's most recent quarterly revenue grew 39% year-over-year, gross margins hit records, and the storage sector began being priced as part of the AI supply chain. Confirming this logic, he bought 500 shares at around $150 and posted his rationale in the company's internal US stock group.
What made me confident to add positions: the 13F filings
Personal conviction needed institutional validation. US regulations require any institution managing over $100 million to disclose its US stock holdings quarterly via 13F filings—a public, legal record. Instead of immediately adding positions, he waited to observe trends over several quarters. When Q3 2025 13Fs were released, he mapped Seagate's institutional ownership over the past year: in late 2024, only about 800 institutions held the stock; by Q2 2025, a clear turning point appeared; by Q3, the count exceeded 1,200, with new entrants increasing each quarter. Although the total position value grew partly due to the stock's appreciation, the breadth indicators—number of holders and new entrants—rose steadily, indicating systematic professional buying rather than a few funds betting. Only at that point did he feel confident to scale up, later adding Seagate ($STX) and SanDisk ($SNDK) via LEAPS CALL options.
Looking back now
On the day of his initial purchase, Seagate closed at ~$150; today it trades around $965, a more than 6x gain—briefly surpassing Palantir as the top S&P 500 gainer of the year. His first 500 shares alone yielded a paper profit of roughly $400,000. That a single hard drive purchase led to a 6x trade still surprises him.
Summarizing the approach
The method is not complicated: everyday anomalies (rising prices, shortages, queues) often provide signals earlier than news or earnings reports. Do not stop at the feeling that something has become more expensive; pull price data to distinguish trend from noise. Then ask whether a long-term structural demand exists behind it, identify the listed company in the key position of the supply chain, and finally verify institutional interest using consecutive quarters of 13F data. Base purchases on logic, not gut feeling.
A final word on risk
This is a successful case. He also has instances where price anomalies turned out to be short-term fluctuations—those trades were not shared in the group, but they were equally real. Survivorship bias is evident. This is a personal review, not investment advice. The core takeaway: pay attention to everyday price signals, dig deeper to find the cause, identify the benefiting listed company, and use 13F data to see if professional money agrees. The next time something you regularly buy inexplicably rises in price, pause and think: who is making that money? Is that company already publicly traded?