Direct cost is traceable to a specific product, including raw materials and direct wages.
Work cost, the sum of prime cost and factory overheads, represents costs up to the factory stage.
First cost typically denotes the initial expense to acquire or produce an asset or product.
These are established terms in cost accounting.
Conversely, Flat cost lacks a formal definition in cost accounting. It is a general term for a fixed or unchanging cost but has no precise technical meaning within cost accounts.
Consequently, Flat cost is the outlier among these terms.