(pronounced ek-STEHN-ded kahst)

Why are we teaching you a boring accounting term? Because you will encounter it on invoices. (Interior design isn’t ALL creative, you know!) In the bookkeeping game, the extended cost is the unit cost — i.e., the cost of the individual item — multiplied by the number of those items that were purchased. For example: Seven chairs purchased at a unit cost of $850 have an extended cost of $5,950.