The hidden fee you pay every trade — and it's not commission

Many apps advertise zero-commission trading, so it feels free. But every stock, ETF, or crypto has two prices at once: the bid (the highest price buyers will pay) and the ask (the lowest price sellers will accept). The gap between them is the bid-ask spread, and it's a real cost you pay the instant you trade.

Here's the catch: when you buy, you usually pay the ask; when you sell, you usually receive the bid. So if a stock has a bid of $100.00 and an ask of $100.05, you're effectively down 5 cents the moment you buy — before the price moves at all. The market maker sitting in the middle pockets that spread as their profit for always being ready to trade.

Spreads are tiny for heavily traded assets like big-company stocks or major ETFs, where millions of shares change hands. But for thinly traded small stocks, obscure options, or low-volume crypto, the spread can balloon to a meaningful percentage of the price. That's why frequent trading in illiquid assets quietly bleeds returns — the cost is baked into the price, not shown as a line item.