TLDR: Mechanics here are incompetent and prices are expensive relative to other places. Avoid.
There was a slow leak in the tube of my tire so clearly something was puncturing the tube. I first changed the tube myself trying to find the source of the leak. I found a little piece of wire stuck in tread. I removed this and slowly about two or three weeks later the tire was flat again. So I figured I should take it in to some professionals. I dropped it off at ABC Cycles and came back four hours later. It cost me around $17 for tube and labour. They said they checked the inside of the tire for glass/debris but didn't find anything, and if the leak happened it probably due to the fact that I need new rim tape.
About three weeks later my tire was flat again. Same slow leak. I took it back to them and described that the same situation was happening. They said I probably rode over some glass. I told them that was unlikely because 1. I hadn't ridden my bike very often in those three weeks, and 2. It leaks very slowly over the course of two days, just like before. Anyway, I politely asked if they would changed it for free and they said no and kept making excuses as to how this third flat was different from the first two. So I left and went to Yeti on St-Laurent and Fairmount. The mechanics at Yeti changed it on the spot (took 15 minutes), found a second piece of wire stuck in the tread (which was causing the leak), and it only cost me $10.