Not surprisingly, Dan Ariely has an anecdote about this (featuring a locksmith): https://www.youtube.com/watch?v=x8baBvOk0ng
Employees with more experience tend to command a higher wage, for exactly the reason you mention — they are more productive, and their time is therefore more valuable.
There is also an anecdote that has been ascribed to multiple people and situations. In its generic form it goes like this: rich person has a problem with a machine, and calls in a relevant repair person, who proceeds to make a trivial intervention (e.g. a few taps with a hammer), and subsequently submits a disproportionately large invoice, considering it took barely a few minutes. When quizzed about this the following detail is provided: “tapping with hammer = tiny amount; knowing where to tap: large amount.”
More detail here: https://quoteinvestigator.com/2017/03/06/tap/