This can work for the provider of a service, in certain circumstances.

But my opinion is that it is always better to charge a price that reflects the value delivered, no matter how long it takes to deliver that value.

There is a (possibly apocryphal) anecdote I read once in which a consultant was brought in to service a machine with many parts. He replaced one part and invoiced (say) $10,000 for replacing a part worth $1. When asked why his bill was so high, he said: "I charge $1 for the replacement part. The other $9,999 is for knowing which part to replace."

As knowledge workers, those who are skilled must remember that "hours spent sitting in a seat" is not a valid measure of their productivity and should not permit clueless managers/clients from judging them in that way.