Conceptual references
Unit pricing
Comparing prices by a common unit — such as kilogram, liter, meter, or item — is used to make it easier to analyze products with different quantities. This principle is set out in Directive 98/6/EC of the European Parliament and of the Council on consumer protection in the indication of the prices of products offered to consumers.
Break-even analysis
It identifies the moment when accumulated savings make up for a larger initial investment. The traditional explanation of the calculation can be found in the Plan your business guide from the U.S. Small Business Administration, which includes a section on the break-even point. In the device-with-refills calculator, this principle was adapted to compare the price difference between the devices with the savings gained on each use.
The “razor and blades” model
It describes situations in which a main product is tied to the recurring purchase of consumables, such as printers and cartridges or coffee machines and pods. The model is discussed in the academic paper Pricing the Razor: A Note on Two-Part Tariffs, published by Richard Schmalensee.
Cost per use
In this tool, cost per use is calculated by dividing the product’s price by the estimated number of uses. It is a practical application that helps take durability into account, but it does not replace a complete analysis of all the product’s costs.
Life-cycle costing
It considers that the purchase price is only one part of the cost of a good. Energy, maintenance, parts, insurance, and disposal can also be part of the total cost. These elements are explained in the European Commission’s guidance on Life-cycle Costing.
Opportunity cost
It represents what we give up when we choose one alternative over another. This concept is presented by Federal Reserve Education and underlies the site’s reflections on planning a purchase, waiting, or setting money aside for another purpose.
These references provide the conceptual basis of the project. The formulas used by the site were simplified and adapted for educational purposes, with the aim of helping consumers make more conscious financial decisions in everyday life.