Given the high price of groceries, this seems like a repugnant scam, particularly in a neighbourhood where many people are struggling to pay their bills.
The other problem, of course, is that this particular Shoppers Drug Mart often has no staff working the cashiers at all. I'm assuming I can't be the only one who has fallen for this scam.
I realized, after way too long, that the discounts were never honoured. Today, I asked an employee why this is and she said customers need to go to a cashier to get the discount, which is actually stated in such small print that most wouldn't notice it.