You're made my point.  Loblaws has chosen to compete on price.  This works for their target niche.  Thrifty Foods competes on quality, but they charge more.  This works for their target niche.

Loblaws/Superstore could pay more for staff, more for better quality produce, etc. etc., but then they'd have to charge more.  And then they'd be targeting people in Thrift's niche.  They don't want to do that cuz it's inconsistent with their corporate strategy.  Their strategy is to target price-conscious customers who are willing to forego certain advantages to save a few bucks. 

There are implications associated with a low-cost strategy, and low wages is one of them.