Most traders absorb the phrase "market maker" early in their education, nod along, and move on. Then one day they're watching a thinly traded stock bounce between $2.40 and $2.55 without a single news event, and it clicks — someone is deliberately sitting on both sides of that trade. That someone is a market maker, and they're not doing it out of generosity.

A market maker is a firm or individual that continuously quotes both a buy price (the bid) and a sell price (the ask) for a security. They commit to transacting at those prices, which means other participants can always find a counterparty. Without them, you'd post an order and wait — sometimes forever — for someone on the other side to show up.

CONCEPTMarket makers earn their profit from the spread — the gap between what they'll buy at and what they'll sell at, repeated thousands of times per day.
WARNINGWide spreads in illiquid securities mean you're paying a hidden cost on every entry and exit — this erodes edge faster than most traders calculate.
KEY IDEALiquidity isn't free — it's manufactured by market makers who take on inventory risk in exchange for capturing the bid-ask spread consistently.

Here's how the mechanic works with real numbers. Imagine a market maker quotes BHP at $45.00 bid and $45.04 ask. A retail buyer pays $45.04. A retail seller receives $45.00. The market maker pockets $0.04 per share on each matched pair. Do that 50,000 times in a session and you've collected $2,000 — before any directional risk. That $0.04 gap is called the bid-ask spread, the market maker's core revenue source.

MARKETMAKERBUYERpays $45.04SELLERgets $45.00SPREAD$0.04/shareBid $45.00 — Ask $45.04 — Spread = $0.04

The risk market makers carry is called inventory risk — if they accumulate too many shares on one side and the price moves against them, the spread revenue won't cover the loss. This is why they constantly adjust their quotes in response to order flow. Understanding this dynamic helps traders recognise why spreads widen during volatile sessions — the market maker is pricing in the extra risk of holding inventory. For deeper reading, the mechanics of market makers on Investopedia covers their obligations thoroughly, the Wikipedia entry on market makers traces their structural history, and Investopedia's breakdown of the bid-ask spread quantifies exactly what liquidity costs retail participants.

Every time you trade, the spread is a toll. Knowing who collects it — and why — changes how you evaluate entry costs, position sizing, and the true friction in any strategy.

This content is for educational purposes only and does not constitute financial product advice. Past performance is not indicative of future results. Profit Logic Ltd (ACN 688 669 936) accepts no responsibility for errors or omissions in this content or anywhere on this website. Always seek advice from a licensed financial adviser before making investment decisions.