A turn of the screw
There was an industrialist whose production line inexplicably breaks down, costing him millions per day.
He finally tracks down an expert who takes out a screwdriver, turns one screw, and then - as the factory cranks back to life - presents a bill for £10,000.
Affronted, the factory owner demands an itemized version.
The expert is happy to oblige: "For turning a screw: £1. For knowing which screw to turn: £9,999."
It is true that work might sound ordinary but knowledge and expertise save a lot when they are a "must" to optimize the job and save money, it has a valuable price as well!:)