If more people eat in a restaurant, the catering cost will increase, although revenue will also increase.
Some examples of indirect costs and their drivers are: indirect costs for maintenance, with the possible driver of this cost being the number of machine hours; or the indirect cost of handling raw-material cost, which may be driven by the number of orders received; or inspection costs that are driven by the number of inspections or the hours of inspection or production runs. In marketing, cost drivers include the number of advertisements, number of sales personnel etc. In customer service, cost drivers include the number of service calls attended, number of staff in service department, number of warranties handled, hours spent on servicing etc..
Porter, M., Competitive Advantage, [page needed] /wiki/Wikipedia:Citing_sources ↩
Strategic Cost Management: The New Tool for Competitive Advantage by Shank and Govindarajan ↩