My favorite backup is an older Singer.
I am not sure there is a lot of $$ in the business. I believe more than they don't dedicate too much time each day to service machines. I have brought mine to a shop that has lines of used machines by the door floor and it looks like they are super busy servicing machines. It turned out that those were machines that people has traded. They keep them there and service them when they can before they sell them, and if they don't get to your on time they point at the row on the floor and how busy they have been. I recently found out that the person that does the work only comes twice a week for a few hours.
At my LQS they gave me the number of a man that comes and do it at your home. He is really nice. His wife stays in he car and reads while he works. I called him a while ago to service my older Bernina because it was noy touched for years. It took him 3 visits and some brushes ordered and he never charged another penny. It was all done for $25.00 and he worked around my husband's schedule.