prime cost

WordReference Random House Unabridged Dictionary of American English © 2025

prime′ cost′, 

1. that part of the cost of a commodity deriving from the labor and materials directly utilized in its manufacture.

• 1710–20

Collins Concise English Dictionary © HarperCollins Publishers::

prime cost noun

1. the portion of the cost of a commodity that varies directly with the amount of it produced, principally comprising materials and labour
   Also called: variable cost
   Compare overheads