Variable Overhead

Let's say you had a flexible manufacturing company: OompaLoompa. Each day, some vague number of workers showed up at your flexi-factory to make candy, based on yesterday's global demand. The volumes changed a lot each day, such that, at times, you only needed 4,000 square feet of factory space, and other days you needed 80,000 feet.

Things varied. The cost of renting that factory space, the support, the heat, the Human (or whatever Oompa Loompas are) Resource director's salary. All of those would vary. If you needed a ton of them, it'd cost you more than if you only needed one. Your overhead will have varied along the way to the teeth-rotting goals you had set out there.