Although apocryphal, it is still a pertinent story. A critical machine in a large factory breaks down, holding up production worth tens of thousands of dollars a day. When the in-house experts cannot fix the problem, the factory manager calls in an external mechanic. For a few minutes, this outside mechanic walks up and down the machine, occasionally poking things with his screwdriver. Then, in a flash, he leans in to tighten a screw and the machine starts up. But the factory manager is less delighted a week later, when an invoice for US $10,000 hits his desk. He rings up to query the amount. ‘That's right,' says the mechanic. ‘It's a dollar for tightening the screw - and 9,999 dollars for knowing which screw to fix.'