Do you know who pays for it when you Price Match @ a Grocery Store ? Surprise !!
The Manufacturer or the Vendor pays the retailer ( Grocery Store ) the difference back, when you price match or ad match a competitor's flyer ! The retailer doesn't absorb the loss , the Vendor/Manufacturer does.
So if No Frills has General Mills Cereals advertised in their flyer for $ 3.00 and you Price Match it at Wal Mart because they are selling it for $ 4.00 .
WM later on bills/invoices General Mills for the difference of $ 1.00 !!..the money they lost on the price match.
They (WM) don't absorb the loss, but force the vendor to do it. They hold them responsible and liable for letting their rival store get it & sell it for a lesser price.
I saw a couple of Senior high level retail analyst talking about this. This is the NORM in the grocery industry in Canada.