I saw the same chart in a shop just two weeks ago here in Fallbrook, except it did not have the bottom line.
I have to say though, when I ran out of time to address an issue on my daily driver 1990 Bronco last December, I decided to cave in and brought it to a specialized shop for older cars in Santa Monica. I told them the issue. $1,100 later, they declared the issue fixed by addressing what seemed to me to be a very unlikely cause. I picked it up and found they had grossly misadjusted the ignition timing, so I fixed that. They did not solve the issue and I am back on deck.
This was my exact experience back in 2000 with my Pagoda. I had a whole bunch of work done to address poor running issues by 3 different vintage Mercedes specialized shops in The Netherlands. Several thousand €€ later, the issues were not fixed. I decided to search the interwebs, found the old Yahoo! Forum, took matters in my own hands and got the car running great.
Then a few years ago, I had an intermittent crank no start issue on our 2008 Volvo. I was unable to find the cause so finally took it to a Volvo specialist. They could not find the cause. Then I took it to a local Volvo dealer: they were unable to find the cause also. I finally sold the car, disclosing the issue to the buyer. A year ago she let me know it was still not fixed despite several shops looking into it.
I've also had good experiences with professional garages but, on the whole, more success doing things myself, with the help of forums and shop manuals. And the savings can be huge, just look at that chart!
