$120 canadian is about $90 US, so Vancouver is doing cheap by US standards. The tiny city I live in reports $102/hour, but I think this is both operative costs and amortized capital costs. You can see the numbers in the reports at https://www.transit.dot.gov/ntd (if you can find them).

The capital costs of the bus isn't that much different over the lifespan of a bus. If you need a large bus at all, then it is cheaper to buy one large bus than both the large and small. Small buses cost less mostly because the drivers don't have to be as well trained - I'm not sure I want that difference.