Ancillary costs refer to additional expenses that are incurred in addition to the main or primary cost of a product or service. These costs are often overlooked or underestimated, but can significantly impact the overall cost of a transaction or project. Examples of ancillary costs include shipping fees, taxes, installation fees, and maintenance costs. These expenses are not directly related to the main cost, but are necessary for the completion or use of the product or service. It is important to consider ancillary costs when budgeting or making purchasing decisions to accurately assess the total cost and avoid unexpected expenses.