I can’t imagine the price of food being that much different that it would be worth hauling groceries up from the States, in fact the price of ice to cool it for the trip might tip the balance.
It is a funny way of looking at economics, anecdotally that is. We buy from the dollar store, and then shake our heads when our great factory job has been off shored. We love the fact that we saved three dollars on a Rapala without considering that we drove three hours and two border crossings for it (or paid to drive to, park at, and pay to get into, a fishing show).
As far as big ticket items go, I bought a boat recently and in doing so made contact with lots of dealers here and in the near States. Every quote that I was given was higher or within dollars from the US dealers (honest). Now used boats may be a different story, because of the situations they were originally purchased under, but those were my findings. Couple that with establishing a relationship with a local dealer for service and warranty benefits, and it makes you reconsider buying a boat cross border.
Thus endith the sermon.