I used to own and operate a retail sign shop... My rent was $3000 a month, plus all the overhead stuff like electricity, insurance, computers, software, equipment, consumables. I had to clear on average about $6500-7000 a month just for the honor of running a business. If my average profit margin on a job was 40% then I had to have $17000 in sales to clear enough profit to cover those fixed expenses. Running a business is a ball buster of a responsibility!
If it weren't for school and institutional bulk jobs I don't see how an instrument repair guy can make a living off walk in retail customers. Especially the the kind that want to yelp him for charging $5 for something! That guy could be PAYING $50+ an hour to keep the lights on, so what does spending 15 minutes on your $5 job cost him? He LOST money!
Go to your car mechanic and see what THEY charge. Those guys have the repair shop business model figured out. They even whack you for "shop supplies" and "waste disposal" based on a percentage of your total bill. It's just a pure markup disguised as a fake fee.
If you want an instrument guy available in your community then you woudl be smark to support them so they can stay in business.