This is 100% crap.
Mechanic - school/education 25-50 thousand dollars + 50-100 thousand dollars in tools and diagnostic equipment. YEARS of experiance!
You come in, need a new timing belt on your car. Book calls for 3.5hrs. Mechanic as the specialty tools and the experiance with this job to complete the task in 2hrs. You, the customer WILL be charged what the book calls for, 3.5hrs. A mechanic should not be PUNISHED just because he has spent the money for the tool and has the experiance required that makes him/her an exceptional Tech.
The book is an estimate of the time an adequate tech with a good supply of tools should be able to complete the task.
Other wise you would be taking your car to the shop. Then they say "sure its 4 hours of labor". THen when you come to get it they say "Wow, that thing was a tough one, looks like you owe us 6hrs because we are no good at our job and dont have the right tools for the job. Thanks for helping us to buy some for the next time your car comes in".
If you are a good tech working at a busy shop thenyou should be able to pull 10-12hrs in a 9hr work day. That is how every shop I have ever heard of works.