Pricing products that must be used along with a main product, such as razor blades for a razor handle or ink cartridges for a printer, is known as:

Explanation

* Captive-Product Pricing sets a low price on the primary durable hardware while applying high profit markups on required supply accessories.
* By-product pricing sells waste/byproducts; Bundle pricing combines products; Optional pricing prices extra add-on accessories.
* This model is widely known in business strategy as the ‘razor-and-blades’ revenue model.