Costs come in several forms, including charges for buying and selling, ongoing annual fees on funds, and platform or account charges. Individually these may seem minor, but because they are taken year after year, they compound against you in the same way that returns compound in your favour. Money paid in fees is money that is no longer invested and can no longer grow.
The effect grows with time. Over a few decades, the difference between a low-cost and a high-cost approach can add up to a meaningful portion of your final balance, even when the underlying investments are similar. This is why many investors pay close attention to costs and favour cheaper options where they can, since fees are one of the few things about investing that are largely within your control.
This content is general information, not investment advice.