I worked as a mechanic at a large dealership in Montreal until 1975 and I know, that to a motorcycle store owner the money was in new unit sales. I don't imagine it's any different now. In this part of the world early spring was high time for sales. Every other aspect of the business would aid to that end, assembling, PDI's, installing accessories (the shop hired guys just for this job in the spring, freed up the mechanics to do our work) and the parts department pushed those sales of accessories, etc.
I also know the owner was happy if the shop showed a profit at the end of the year. And we were busy. I think the idea for the rest of the year was that the shop helped make money for the parts department, and lets face it there was big money in parts sales too. I was never comfortable knowing this.
There was a full time core group of people of course, but it seemed there was always a transient labour force in that business, so I think the wages were lower because of that. It's just the way the business worked. I will say too there was an attempt to offer good service in those days. I was paid an hourly wage and....basically starved, it was a long time ago.
Still in 75 I moved to Vancouver, BC and the scene was somewhat different, less population than in the east, sales weren't as brisk and I worked in a small business that laid more focus on the shop because he sold fewer bikes. It was a real "service department" and we made good service a priority. I worked for 45% of the shop rate. If I made a mistake I made good on my own time so you had to be careful, but if you were fast the money was really good.
A month after moving three thousand miles I averaged $400/week compared to $125 in MTL. Not bad in those days.