Every Costco trade has a cost, and understanding those costs is essential to long-term profitability. The main cost is the spread — the difference between the buy (ask) and sell (bid) price of Costco. A tighter spread means you cross less distance to break even, which matters most for active traders who place many Costco trades each day. Spreads on the Shares market widen during volatile or illiquid periods, so timing matters.
Depending on the account type, you may also pay a commission per trade instead of, or in addition to, a wider spread. Raw-spread accounts typically offer very tight Costco spreads plus a fixed commission, which often works out cheaper for high-volume traders. If you hold a Costco position overnight, a swap (financing) charge or credit is applied to reflect the cost of leverage — this can add up on longer-term trades.
To keep your Costco trading costs under control, trade during the most liquid sessions when spreads are tightest, choose an account type that matches your volume, and factor overnight swaps into any position you plan to hold for days or weeks. Vantage offers competitive, transparent pricing on Costco so you always know what you are paying.