Q: I think I was way overcharged for repairs.

Whether or not you were overcharged depends largely on what the labor rate is where you went. The cost per labor hour can be anywhere from $70 per hour in a small rural town shop to over $180 per hour at a major dealership in a big city. Most shops use a standard labor guide, which specifies how many labor hours should be charged for a specific job. As for parts, the EVAP canister most likely had to be a dealer part and the cost would be high if they are only supplier. Diagnosis is the cost to diagnose most problems and you had three problems– two fault codes and the tensioner issue. I would need more details of labor rates and location of repair to know if you were truly overcharged, though from the sound of it, you likely were not. Traditional repair shops have a lot of overhead costs. Next time, you can try using YourMechanic, which offers labor rates significantly lower than competing dealerships and shops.