Murabaḥah is a term for a sales contract where the buyer and seller agree on the markup, the ratio between the cost of a good or service and what?
Markup (business) Markup is the ratio between the cost of a good or service and its selling price. It is expressed as a percentage over the cost. A markup is added onto the total cost incurred by the producer of a good or service in order to cover the costs of doing business and create a profit. The total cost reflects the total amount of both fixed and variable expenses to produce and distribute a product. Markup can be expressed as a fixed amount or as a percentage of the total cost or selling price. Retail markup is commonly calculated as the difference between wholesale price and retail price, as a percentage of wholesale. Other methods are also used.
Sürsat Sürsat was a form of food requisitioning with price controls, used by the Ottoman Empire to provide consumables for its armed forces. It was related to nüzül; sürsat was initially an obligation for the public to provide food and other supplies at a pre-fixed price which was unlikely to be favourable, or might even be merely symbolic. Istira was basically the same obligation, but supposedly at "market" price. Over time, nüzül, sürsat, and istira were all transformed into extraordinary cash taxes on people living near the route travelled by the army.