Not that long ago, buying or selling a stock came with an obvious price tag. A trade might cost $20 or $30. Then it became $9.95. Then $4.95. Today, at many brokerage firms, it costs $0.
That is real progress. Lower transaction costs have made investing more accessible and removed an expense that once made smaller trades particularly inefficient. But somewhere along the way, “commission-free” became synonymous with “free.” Those aren’t the same thing.
It’s not as if Wall Street suddenly decided to stop making money.
When the Price Disappears, Follow the Economics
When you place a stock trade, your order has to go somewhere to be executed. Depending on the brokerage and the type of order, it may be routed to an exchange, an electronic trading venue, or a market maker.
In some cases, market makers pay brokerage firms for that order flow. This practice—appropriately called “payment for order flow”—can help support a business model in which the investor pays no explicit trading commission.
Importantly, payment for order flow does not automatically mean an investor received a bad price. Brokerage firms are still subject to “best execution” obligations requiring reasonable diligence to obtain favorable execution for customers. But it does create an economic relationship behind a transaction that appears free to the investor. And that distinction matters.
A $0 Trade Can Still Have a Cost
Imagine an investor wants to buy 1,000 shares of a stock trading around $50. The value of the purchase is approximately $50,000. The brokerage commission?
$0.
But suppose the investor’s execution price is just two cents per share less favorable than another reasonably available outcome. Two cents sounds trivial.
Across 1,000 shares, however, it represents $20. If a similar difference occurs when the position is eventually sold, the round trip represents $40 of additional trading friction.
That does not mean every commission-free trade costs $40, nor can a worse execution automatically be blamed on payment for order flow. Market prices move constantly, spreads vary, and execution quality depends on a number of factors.
The point is simpler: the commission printed on the confirmation is not the only economic consideration in a trade.
Scale that across a portfolio and small differences can add up. An investor with a $500,000 account who generates $400,000 of combined buying and selling activity during a year would incur $400 of trading friction if spreads and execution differences averaged just 0.10% of the dollars traded.
The statement could still show $0 in trading commissions.
But the Bigger Cost May Be Behavioral
There is another consequence of free trading that is harder to quantify.
It makes trading feel free.
When every transaction came with a $20 commission, investors had a reason to ask whether a trade was really necessary. Today, buying or selling can take a few taps on a phone with no visible cost attached.
That convenience is useful when a trade actually needs to be made.
It can be expensive when it encourages activity for activity’s sake.
Selling an investment after a bad week, chasing the stock or sector that just went up, constantly repositioning a portfolio around headlines, or realizing taxable gains without considering the tax consequences can create costs that dwarf a commission or a few cents of execution difference.
A trade that costs $0 can still be a very expensive decision.
Free Is a Price. It Is Not a Strategy.
None of this is an argument for bringing back $20 trading commissions.
Lower transaction costs are generally a good thing. Investors should be able to rebalance a portfolio, invest new savings, harvest losses, or make other prudent changes without worrying that every click carries a large fee.
But removing the explicit cost of a transaction does not remove its consequences.
Investors should understand how their brokerage makes money, pay attention to execution quality, and—most importantly—have a reason for trading beyond the fact that they can.
Because the real question is not whether a trade costs $0.
It is whether making the trade actually improves the plan.