I agree with the others as well. Mark up percentage depends alot on the parts. For service we charge an hourly rate and mark up most parts to retail, some are arked up more and others are barely marked up at all though. A thing we keep in mind is the likelyhood of a future service call for warentee work on the part. If it is something that has a high liklyhood that we will need to replace it under warentee down the road, then there may be a higher likelyhood that we charge a higher markup to help cover the future anticipated costs.
Why do people not respect us as they do other tradesmen? Because every Tom, Dick, and Harry doesn't think he can be a plumber or electrician!