Many years ago, store were advertising prices really low just to lure people into their store. Then, when you got there, they claimed it was a typo & charged the full price. I think they called it bait & switch. So, laws were passed that it was the store’s responsibility to advertise the correct price & IF they failed to do so, they were legally bound to sell it at the cheaper price. This was back when stores put price labels on the items & there were price labels on the shelves. I went into a store one day where a $10 item was marked on the shelf & the item itself at 1ยข. The store manager wasn’t happy, but I left with my item for a mere penny!!!
Then people got greedy & started switching those labels with their own price. Once stores became aware of this, they STOPPED honoring the price deal as well as prosecuting those switching labels with shoplifting!!! A few stores charged their loss to the stock clerk who made the error to begin with.
I don’t know the law in Canada, but it should be close to the same.