The amount that a manufacturer, supplier, or retailer adds to the cost of a product or service. The mark-up percentage is calculated based on each company's own formula, taking into account factors such as overhead, operating expenses, advertising budget, and other such considerations. Keystone mark-up or keystoning are terms which indicate that an item has been marked up to double the cost.
See also Markdown.
Historical Dictionary of the Fashion Industry. Francesca Sterlacci and Joanne Arbuckle.