Question: 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?

Context articles: Land contract
Murabaha
Output contract
Formula pricing
Order (business)
Markup (business)
Call option
Lost volume seller
Incoterms
Point of total assumption

A land contract — often described by other terminology listed below — is a contract between the buyer and seller of real property in which the seller provides the buyer financing in the purchase, and the buyer repays the resulting loan in installments.
 Under a land contract, the seller retains the legal title to the property, while permitting the buyer to take possession of it for most purposes other than legal ownership.
 The sale price is typically paid in periodic installments, often with a balloon payment at the end to make the timelength of payments shorter than in the corresponding fully amortized loan (i.e., a loan without a final balloon payment).
 When the full purchase price has been paid including any interest, the seller is obligated to convey (to the buyer) legal title to the property.
 An initial down payment from the buyer to the seller is usually also required.
Murabaḥah, murabaḥa or murâbaḥah (Arabic: مرابحة‎ ‎ , derived from "ribh" Arabic: ربح‎ ‎ , meaning profit) is a term of "fiqh" (Islamic jurisprudence) for a sales contract where the buyer and seller agree on the markup (profit) or "cost-plus" price for the item(s) being sold.
 In recent decades it has become a term for a very common form of Islamic (i.e. "shariah compliant") financing, where the price is marked-up in exchange for allowing the buyer to defer payment (a contract with deferred payment being known as "bai-muajjal").
 "Murabaha" financing is similar to a rent-to-own arrangement in the non-Muslim world, with the intermediary (i.e. the lending bank) retaining ownership of the item being sold until the loan is paid in full.
 There are also Islamic investment funds and sukuk (Islamic bonds) that use "murabahah" contracts.
An output contract is an agreement in which a producer agrees to sell his or her entire production to the buyer, who in turn agrees to purchase the entire output.
 Example: an almond grower enters into an "output contract" with an almond packer: thus the producer has a "home" for output of nuts, and the packer of nuts is happy to try the particular product.
 The converse of this situation is a requirements contract, under which a seller agrees to supply the buyer with as much of a good or service as the buyer wants, in exchange for the buyer's agreement not to buy that good or service elsewhere.
In commodities transactions, formula pricing is an arrangement where a buyer and seller agree in advance on the price to be paid for a product delivered in the future, based upon a pre-determined calculation.
 For example, a packer might agree to pay a hog producer the average cash market price on the day the hogs will be delivered, plus a 2-cent per-pound premium.
In business or commerce, an order is a stated intention, either spoken or written, to engage in a commercial transaction for specific products or services.
 From a buyer's point of view it expresses the intention to buy and is called a purchase order.
 From a seller's point of view it expresses the intention to sell and is referred to as a sales order.
 When the purchase order of the buyer and the sales order of the seller agree, the orders become a contract between the buyer and seller.
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.
A call option, often simply labeled a "call", is a financial contract between two parties, the buyer and the seller of this type of option.
 The buyer of the call option has the "right, but not the obligation", to buy an agreed quantity of a particular commodity or financial instrument (the underlying) from the seller of the option at a certain time (the expiration date) for a certain price (the strike price).
 The seller (or "writer") is obligated to sell the commodity or financial instrument to the buyer if the buyer so decides.
 The buyer pays a fee (called a premium) for this right.
 The term "call" comes from the fact that the owner has the right to "call the stock away" from the seller.
Lost volume seller is a legal term in the law of contracts.
 Such a seller is a special case in contract law.
 Ordinarily, a seller whose buyer breaches a contract and refuses to purchase the goods can recover from the breaching buyer only the difference between the contract price and the price for which the seller ultimately sells the goods to another buyer (plus, under some circumstances, incidental damages).
The Incoterms rules or International Commercial Terms are a series of pre-defined commercial terms published by the International Chamber of Commerce (ICC) relating to international commercial law.
 They are widely used in International commercial transactions or procurement processes as the use in international sales is encouraged by trade councils, courts and international lawyers.
 A series of three-letter trade terms related to common contractual sales practices, the Incoterms rules are intended primarily to clearly communicate the tasks, costs, and risks associated with the transportation and delivery of goods.
 Incoterms inform sales contract defining respective obligations, costs, and risks involved in the delivery of goods from the seller to the buyer.
 However, it does not constitute contract or govern law.
 Also it does not define where titles transfer and does not address the price payable, currency or credit items.
The point of total assumption (PTA) is a point on the cost line of the profit-cost curve determined by the contract elements associated with a fixed price plus incentive-Firm Target (FPI) contract above which the seller effectively bears all the costs of a cost overrun.
 The seller bears all of the cost risk at PTA and beyond, due to a dollar for dollar decrease in profit beyond the costs at the PTA.
 In addition, once the costs on an FPI contract reach PTA, the maximum amount the buyer will pay is the ceiling price.
 Note, however, that between the cost at PTA and when the cost equals the ceiling price, the seller is still in a profitable position; only after costs exceed the ceiling price is the seller in a loss position.