I think it is easy to under value the service that most garages \ specialist provide considering the amount of investment in tooling , diagnostics , information and training that is required there doesn't seem to be many industries that have this on going commitment yet their charges are often far greater than the garage trade. Personally i carry out dealer labour rate surveys each year locally and average out the labour rate i try and charge 70% of this as my rate seems to work for my business and is a good marketing tool if customers say that you are expensive.