In August last year, a former ByteDance employee (Leto Bao) set up a personal quantitative trading platform and bought two Seagate hard drives from Pinduoduo. That seemingly mundane purchase became the starting point of a remarkable investment journey. He shared all trade details, cost basis, and P&L in the company’s US stock group; this is his complete post-mortem.
Hard Drive Prices Changed Daily
After the drives arrived, he noticed the same model from the same store saw multiple price increases within a week, with no decline. Such a sustained one-way price rise is highly abnormal for a high-volume, standardized industrial product. Using price comparison tools like Manmanmai and Keepa, he pulled historical price curves for that drive and other high-capacity models from Seagate and Western Digital. The conclusion was consistent: the entire high-capacity mechanical hard drive product line was experiencing continuous, one-way price increases, not short-term promotion volatility. This confirmed there was a larger underlying driver.
Tracing Down: AI Was Hogging Hard Drives
Unraveling the logic: the market focuses excessively on GPU demand from AI, but large model training and inference generate massive data requiring long-term, low-cost storage, which relies on high-capacity mechanical hard drives (nearline enterprise HDDs). Cloud giants like Microsoft, Amazon, Google, and Meta are bulk buyers. Seagate’s HAMR technology boosts per-drive capacity, precisely matching data center needs. With limited production capacity, vendors prioritize higher-margin enterprise orders, squeezing retail supply. This caused the Pinduoduo price hikes. Seagate’s quarterly earnings at that time showed 39% revenue growth and record gross margins; the market began pricing the storage sector as part of the AI supply chain. After confirming the thesis, he bought 500 shares at around $150 and posted his rationale, cost, and position in the internal US stock group.
13F Filings Made Him Confident to Add
Personal conviction needed institutional validation. US 13F filings require institutions managing over $100 million to disclose US stock holdings quarterly — a legal, public record of institutional portfolios. He did not add immediately but waited for multi-quarter trends. By the Q3 2024 13F release, plotting Seagate’s institutional ownership over the past year revealed a clear pattern: in H2 2024, about 800 institutions held the stock, with a slight decline; Q2 2025 saw a clear inflection; Q3 accelerated, with institution count rising from 800+ to 1,200+, and the number of new institutions increasing each quarter. Although market cap growth partly came from price appreciation, breadth indicators like institution count and new positions were sequentially increasing, indicating a systematic inflow of professional money. Confirming this, he added heavily and later used LEAPS calls to increase positions in $STX and $SNDK.
Looking Back
On the day he bought the hard drives, Seagate closed at ~$150; today it trades at ~$965, a 6x increase, briefly surpassing Palantir as the S&P 500’s top performer in 2024. The initial 500 shares alone yielded a paper profit of ~$400,000. Two hard drives led to this trade — an unexpected outcome.
Summarizing the Approach
The core methodology is straightforward: stay alert to daily anomalies (price hikes, shortages, queues) — they often provide first-hand signals earlier than news or earnings reports; plot price curves to distinguish trends from noise; ask whether the anomaly reflects a long-term structural demand shift, then identify the publicly listed company at the key node in the supply chain; finally, verify institutional sentiment using 13F filings over consecutive quarters rather than a single quarter. This process does not guarantee success but bases buys on logic rather than gut feeling.
Risk Disclosure
This was a winning trade. He has also tracked price signals that turned out to be short-term noise — those losses were not shared, so survivorship bias is evident. This is a personal review, not investment advice. The takeaway: next time a product you regularly buy inexplicably rises in price, consider who is capturing that profit and whether that company is listed.