"Free" Trading Isn't Free. Here's What You're Actually Paying.
The financial system takes a cut of your money at every layer. Most of it is invisible and that's by design.
When Robinhood and every other major brokerage eliminated trading commissions a few years ago, it felt like a revolution. The $7 per trade went away, and with it the mental math about whether a small purchase was even worth the fee. Opening an app and tapping a button became all it took to call yourself an investor.
Except it wasn’t free. The fees didn't disappear when commissions went to zero, they just went underground. Which is worse in some ways, because you never think to question a cost you can't see.
I spent two years working inside this system as an equity research analyst, and I saw how the revenue streams work from the inside. What struck me wasn't that the system is corrupt, because it mostly isn't. It's that the system is brilliantly designed to extract money from retail investors at every layer while making each layer feel either free or insignificant.
Let me walk you through where your money actually goes.
Layer 1: Payment for order flow
When you place a trade on Robinhood, Schwab, Fidelity, or any other zero-commission brokerage, your order doesn’t go directly to the stock exchange. Instead, your broker sells your order to a market maker (a firm that specializes in executing trades).
This is called payment for order flow, or PFOF. The market maker pays your broker a small fee (fractions of a penny per share) for the right to execute your trade. In exchange, the market maker fills your order and earns the spread: the tiny difference between the price they buy the stock at and the price they sell it at.
How much money are we talking about? In the first nine months of 2024 alone, the largest market maker paid over $940 million to retail brokers for their order flow. These aren’t rounding errors. This is a multi-billion-dollar industry built entirely on routing your trades.
Here’s the uncomfortable question: if the market maker is paying your broker for the privilege of executing your trade, and the market maker is making money on the spread... who’s on the other side of that equation?
You are. You're paying for "free" trading through slightly worse execution on every trade. Each individual instance is small enough that it never registers, and over a lifetime of investing, the total is anything but small.
"Small per trade" and "small in aggregate" are very different things, and the bigger issue here isn't the per-trade cost. It's the incentive structure: your broker's revenue depends on you trading as frequently as possible. Every time you buy or sell, they get paid.
This is why trading apps are designed to feel like games. The push notifications and the confetti animations aren't accidents. The interface is built to make trading feel fun and frictionless, because every time you trade, your broker gets paid. What's actually being sold is volume, and the "free" framing is the marketing.
The brokerage industry made a calculated bet: eliminating the visible $7 commission would dramatically increase trading volume, and the invisible PFOF revenue from that increased volume would more than compensate. They were right.
Layer 2: Fund expense ratios
If you own any mutual fund or ETF (and if you have a 401(k), you almost certainly do), you’re paying an expense ratio. This is an annual fee, expressed as a percentage of your total investment, that covers the fund’s management, administration, and operating costs.
The part that used to infuriate me when I first learned it: you never see this fee on a statement. Instead of being deducted from your account as a line item, it's pulled out of the fund's returns before those returns are reported to you. A fund earns 10%, the expense ratio is 1%, your statement shows 9%. By the time you see the number, the fee has already happened, and unless you went looking for it, you'd never know it existed.
Expense ratios vary enormously, and the difference matters more than almost anyone realizes:
A broad market index ETF (the kind that simply tracks the S&P 500) might charge 0.03%. That’s $3 per year on a $10,000 investment. On a $500,000 portfolio, that’s $150 per year. Negligible.
An actively managed mutual fund might charge 0.50% to 1.00% or more. On that same $500,000 portfolio, a 1% expense ratio costs you $5,000 per year, every year, regardless of whether the fund actually beats its benchmark. Statistically, most years, it won't.
Then there’s another layer that most people never encounter unless they’re reading the fine print: sales loads. These are upfront fees of 3 to 5% deducted when you purchase shares. If you invest $10,000 in a fund with a 5% front-end load, only $9,500 actually gets invested. The other $500 goes to the broker who sold you the fund.
This is the financial equivalent of paying a cover charge to walk into a restaurant and then also paying for the meal. The load is a commission in disguise. If anyone ever tries to put you in a fund with a sales load, that’s your signal to ask hard questions about why they’re recommending that specific product.
Loads have become less common as investors have migrated toward no-load index funds and ETFs, but they still exist, especially in funds sold through traditional financial advisors and bank wealth management programs. Which has me noticing a pattern: the more "full-service" the financial relationship, the more layers of invisible fees tend to be baked in.
Layer 3: Cash sweep
This is the one that really got under my skin when I started understanding how brokerages actually make money.
The uninvested cash sitting in your brokerage account is making your broker a fortune. When you sell a stock and the proceeds sit in your account, or when you deposit money that you haven’t invested yet, that cash doesn’t just sit in a vault. Your broker “sweeps” it into money market funds or bank deposit accounts and earns interest on it.
How much does your broker earn? Typically at or near the prevailing money market rate, so 4 to 5% right now. How much do they pass along to you? Often 0.01% to 0.10%.
The math on this is genuinely offensive when you see it written out. On a $50,000 cash balance, your broker might earn $2,000 to $2,500 per year in interest while paying you somewhere between $5 and $50. That spread is pure profit, and you'd never notice it because you weren't thinking of that cash as an investment in the first place.
This is one of the largest revenue sources for many brokerages. It’s the quiet engine behind the “free” trading model: they don’t need to charge you commissions because they’re earning substantial returns on your idle cash.
The fix is simple: don’t leave large cash balances sitting in your brokerage account. If you need a cash reserve, put it in a high-yield savings account where you’re earning 4 to 5% instead of 0.01%. Only keep in your brokerage what you’re planning to invest in the near term.
Layer 4: The behavioral tax
The last layer isn't a fee anyone charges you. It's one you charge yourself through bad behavior, and it makes everything else on this list look like pocket change.
Every layer of the financial system is designed to encourage activity. More trades, more fund switches, more reactions to market news. The push notifications and breaking news alerts and "your stock is moving" updates are all engineered to make you feel like you should be doing something.
The correct response to almost all of it is to do absolutely nothing. Which, of course, generates zero revenue for anyone, which is why nobody in the financial industry will ever tell you that.
The data on this is devastating. Study after study shows that the average investor dramatically underperforms the funds they invest in. Not because the funds perform poorly, but because the investor buys and sells at the wrong times. They buy after a run-up, when prices are high, and sell after a downturn, when prices are low. They chase last year's best-performing fund, then panic during the next correction and sit on the sidelines during the recovery that follows.
The gap between “fund returns” and “investor returns” is called the behavior gap, and it typically costs investors 1 to 2% per year in lost returns. I want to make sure you feel how much that is. On a $500,000 portfolio over 30 years, a 1.5% annual behavior gap costs you roughly $600,000 in foregone wealth.
Six hundred thousand dollars, and not because someone charged you a fee or put you in a bad fund, but because at some point you got a push notification that made you nervous and clicked "sell" at the wrong moment.
That’s more than all the expense ratios, PFOF, and cash sweep fees combined. The most expensive fee in all of investing is your own behavior, and the entire system is designed to make that behavior worse.
The total cost of being a retail investor
Let’s add it all up for a typical scenario. Say you have a $200,000 portfolio, you trade moderately, and you’re in a mix of funds:
Payment for order flow: Small per trade, maybe $20 to $50 per year total for a moderate trader. Individually trivial.
Fund expense ratios: If you’re in actively managed funds averaging 0.50%, that’s $1,000 per year. If you’re in index funds at 0.03 to 0.10%, it’s $60 to $200. The difference over 30 years is staggering.
Cash sweep: If you keep $20,000 uninvested, your brokerage might earn $800 to $1,000 on it while paying you $2 to $20. That’s $800+ per year in value you’re leaving on the table.
The behavior gap: If you trade reactively and chase performance, the cost is potentially 1 to 2% annually. That’s $2,000 to $4,000 per year on a $200,000 portfolio. By far the largest line item.
Add it up and the total cost of being an average retail investor is somewhere between 1.5% and 3% per year, almost all of it invisible and, what's more frustrating, almost all of it avoidable.
How to pay as little as possible
The irony of all of this is that the cheapest, simplest approach is also the one that produces the best long-term results. The substantive version of “pay less” comes down to four moves.
Use low-cost index funds. A total stock market index fund with a 0.03% expense ratio captures the entire market’s returns for practically nothing, and you’re not paying a team of portfolio managers to underperform their benchmark.
Don’t leave large cash balances in your brokerage. Keep your emergency fund and short-term cash in a high-yield savings account, and only put money in your brokerage that you intend to actually invest.
Trade as little as you can stand to. Every trade generates revenue for someone other than you, and the less you interact with your portfolio, the better it tends to perform, which is genuinely counterintuitive until you understand the fee layers above.
Ignore the noise. Financial media, push notifications, earnings reports, and market commentary are designed to make you feel like you need to act. You almost never need to act, and the less activity you generate, the more of your money actually compounds.
I turned off portfolio notifications on my phone about three years ago, and it's been one of the best financial decisions I've ever made. The market kept moving, obviously. I just stopped reacting to it, and that turned out to matter more than any fund switch I ever considered.
What to read next
📖 The Simple Path to Wealth by JL Collins. The clearest argument for why low-cost index investing beats everything else for the vast majority of people. After reading this article, you understand the “why.” Collins gives you the “how.”
📖 The Psychology of Money by Morgan Housel. The behavior gap (Layer 4) is really a psychology problem, not an information problem. Housel explains why even smart, well-informed people make terrible investment decisions, and what to do about it.
📖 Thinking in Bets by Annie Duke. A framework for making decisions under uncertainty that directly addresses the impulse to trade reactively. If you’ve ever panic-sold or FOMO-bought, this book is for you.
🎧 All three are excellent on Audible. The free trial gives you one credit to start.
As an Amazon Associate, I earn from qualifying purchases.