Estimates for inspections and maintenance ???

Hello together, in other threads the topic “inspection costs” has been discussed several times. It is striking for me that the costs for standard work and materials (especially oil) partly differ very strongly between the different workshops and also brands. Therefore, it would be important to have a cost estimate for regular inspection and maintenance work. I myself have never done this – honestly – before. But that was perhaps a mistake. Therefore question in the round: How do you keep it with such cost estimates? Let us create some? If so, how do the (Volvo) workshops react? Do you have the impression to have saved money with cost estimates? How are your experiences? Greetings + a nice weekend Hugo