I know of a repairman that is on the plane almost daily and most weeks of the year. Only rarely is he in his hometown to do hometown repairs. He fixes a specific type of equipment, mostly located in cities and where he only needs about two heavy suitcases worth of parts and tools. Some parts are Fedex'ed to customers for him to install.
There is a $2000 trip charge. My guess is the average repair is $4000. The new price of the machine is $50,000 to $80,000.