Places like Creative Bricks and Blocks sell topsoil by the yard (ie it fills a pickup truck), but they also sell smaller quantities. I often see people at the big topsoil bin filling their own bag or bucket for smaller gardens.

A whole truck load of soil is like $45 so a small quantities will be absurdly cheaper than buying pre-bagged soil from a retail store.

There’s also lots of local garden centres that sell bagged soil. GardenWorks has been a go-to for me for years. They’re generally priced close to the big box stores and have a wider selection of soils.

Another option are nurseries. I go to Sun Tai Tsang farms in Burnaby in the spring to buy plants and they always have a good selection of bagged soil, and they’re usually cheaper than retail stores on practically everything they sell. Cheap local eggs too!