The price of commodity coffee is set on the New York Mercantile Exchange for Arabica and on the London Mercantile Exchange for Robusta.
The standard price for Arabica is cents per pound (about 453g), and for Robusta it is dollars per ton (1,000kg).
In reality, coffee importers and producer-exporters often make contracts to purchase a certain amount of coffee of a specific quality over a specific period, such as the next three years.
This is called a forward contract.