Service is more important than profits. Of course, profits are important for the health of the business, but profits are not the sole or even the major focus of the business. Profits are used as a means to an end and are not the end goal. A co-op is a social organization. Cooperation among cooperatives is essential.
Supermarkets generally have a higher markup and larger overhead than co-ops.
Because profit is the main focus of these businesses, you can be assured that any and all increased expenses will be passed on somehow to the customers.