My former employer phoned me up the other day and said he really needed my expertise once again. They had a problem with one of their machines and they had tried everything possible to try and solve it, but to no avail.
Reluctantly I took the job. I spent a whole day studying the problem. Finally I marked a small “x” in chalk on part of the machine and said “this is where your problem is”. They replaced that part and it solved their problem, and so I sent them an invoice for 10000.
They demanded an itemised bill showing how I calculated the cost, so I sent them a new invoice:
One chalk mark: 1
Knowing where to put it: 9999