While controversial, payment for order flow (PFOF) is far more cost-effective for Robinhood's core user base making small trades. A $1,000 trade might incur 200 basis points in old commission costs versus just 1-2 basis points under PFOF. This model makes investing accessible for smaller accounts that would be penalized by flat fees.

Robinhood faced criticism for its Payment for Order Flow (PFOF) model. However, legacy brokers were already using PFOF *in addition* to charging customers a ~$10 commission. Robinhood's innovation was simply eliminating the customer commission, which was 10x larger than the PFOF rebate.

In opaque markets like hay, middlemen (brokers) profit from information asymmetry. Platforms like Haywire, which introduce price transparency, reduce the broker's informational edge, making it harder for them to capture large margins on deals made "blindly."

Large custodians resisted offering fractional shares not due to technical limits, but likely as a business decision. This forced higher idle cash balances (for float revenue) and pushed clients towards mutual funds, which paid hefty distribution fees and were the only fractional-share-like option available.

Brokers offering "zero commission" trades often profit from 'payment for order flow,' which can lead to suboptimal execution prices for customers. Platforms like Interactive Brokers Pro prioritize best execution, resulting in lower all-in costs despite a nominal commission, revealing the hidden price of "free."

The decision to offer zero-commission trades was not an incremental price reduction; it was a fundamental shift in the business model. The team intuitively recognized that "free" possesses a unique marketing power far stronger than a nominal fee. This is key for any company aiming for mass-market disruption.

Robinhood's zero-commission model was viable because it sidestepped the massive customer acquisition costs (CAC) of its competitors. In 2016, incumbents like E-Trade were spending over $1,000 per customer on marketing, while Robinhood's viral growth made its CAC effectively zero.

IBKR's low-cost, tech-first model is strategically counter-positioned against high-touch incumbents like Charles Schwab. Adopting IBKR's model would require competitors to cannibalize their profitable existing business models, creating a powerful competitive moat based on the innovator's dilemma.

While free trading was the hook, the core investment thesis was an arbitrage play. Robinhood could acquire users for free through viral loops while incumbents like Schwab were spending $150 per customer, creating a massive competitive advantage.