My parents own a place in Canada (NB not QC, full disclosure), but it's also worth mentioning that lots of things are slightly more expensive in Canada. I'm not sure about Costco prices in Canada, but I'm not sure you'd get much savings.

Also the U.S. has tightened up rules about brining in produce, so I'd double check that before buying any of those.

Given the time it can take to cross a bigger border crossing, it probably will make it less efficient.