RhymeZone: oncost definitions

Definitions of oncost:

noun: Additional costs; extra expenses.
noun: (finance) Overhead (expense)
noun: (coal-mining) The cost of upkeep, making and maintaining shafts, roads, pumping, etc.
noun: (UK dialectal, Scotland) The indirect expenditure incurred for the purpose of increasing the productive power of organised labour.

(Definitions from Wiktionary)