I can't legally very much beer or wine back to Saskatchewan when I make a trip to Alberta, even though it's significantly cheaper there.
Edit: I knew about the "no transport between provinces" thing, but I didn't know about the receipt thing. I suspect that if you're in Alberta, with Alberta plates, you're not going to have your beer confiscated. If you're in Saskatchewan with Alberta plates, and have a trunk full of beer... they're probably going to suspect you bought it all cheap at home and are bringing it to friends.
Coincidentally, that restriction was just removed! The Minister for Intergovernmental Affairs announced it today. [1]
However, provinces and territories can still legislate their own barriers. But federally, the law no longer stands.
[1] https://www.canada.ca/en/intergovernmental-affairs/news/2019...