To understand cost in economics you'll learn topics like externalities (positive and negative) as well as internalities and their meaning. You'll dive into concepts like opportunity cost as well as fixed vs sunk costs.
Once you get at truly what cost means to an economist you will be so much better informed in making business and personal decisions. In my line of work (software development) so many products and daily decisions hit the sunk cost fallacy of wanting to hang onto projects we are in love with. Other ideas like negative externalities really are the underpinning of understanding why climate change is out of control.
Cost is always oversimplified. Spending some time to understand it deeply and learn the concepts and common language is incredibly valuable.