For me, on flights to Canada, the $25 I pay for a carton of cigarettes (for my mom) is definitely less than the $60 she pays for a carton. Booze, too, is about half the price. I can get a $15 bottle of liquor that will cost $25 or more in the liquor board. MSP's duty-free is the one I frequent most often.
EDIT: To add, for perfumes and such, you're better off buying online from a reputable seller, like scentiments.com