What type of expense is primarily affected by changes in sales volume for an online retail business?

The cost of shipping is primarily affected by changes in sales volume for an online retail business because it is directly tied to the quantity of goods sold. As sales volume increases, the number of packages that need to be shipped also rises, leading to a proportional increase in shipping expenses. Conversely, when sales volume decreases, fewer shipments are made, thereby reducing shipping costs.

This variable nature of shipping costs makes it essential for online retailers to monitor and manage these expenses closely in relation to their sales performance. While other types of expenses, such as operating expenses and marketing expenses, can also fluctuate due to increased sales, they do not have the same direct and immediate correlation with each sale as shipping does. Fixed costs remain constant regardless of sales volume, which further highlights the significance of shipping costs in this context.