We have co-op in Manitoba as well, and their prices seem close-ish to Sobeys and Safeway. Or at least close enough that it's not worth travelling further to get to those other stores. (Couldn't tell you about superstore or Walmart, I refuse to give money to those assholes).

We do a Costco haul every 4-6 weeks, and also go to the co-op at least once a week. Mostly for perishables, and whatever deals they have in their weekly flyer. And for their very good selection of local/Canadian items.