The answer is.. The person who knows the most. A smart friend of mine once told illustrated this to me in this example: A guy calls a mobile computer technician to fix his computer after trying everything he knew to solve the problem himself. The tech shows up, hits a couple of keys, flips the computer around, pulls out a screwdriver and turns a screw half a turn. Immediately, the computer starts working again. The gentleman with the newly repaired computer says "Wow, that was quick work. How much do I owe you?" The tech says, "that will be $100." Surprised, the customer says, "A hundred bucks for turning a screw!?" the tech responds "No sir, that would be outrageous. I charge a dollar for turning the screw. The other $99 is for knowing which screw to turn."
The real story is that the folks who know the most have already put in thousands of hours of time. This is how they acquire the knowledge it takes to earn the seemingly outrageous (to some people) sums of money for each actual hour on the job.