Honestly, our prices up here are all over the map. And they're often higher than yours, for exactly the same things.
Gas, for example, might be C$1.33/L in BC, and right next door in Alberta C$1.09/L. That's US$4.02/US gallon in BC, and US$3.30 in Alberta.
The exchange rate is currently 1 US$ = 1.251 C$, so you think you're getting a deal when you come up here with US$, but if the same stuff you buy in the US is marked up 30% or more, the exchange rate difference is negated. You pay more for the same things up here.
Most of our provinces (except Alberta) have a provincial HST on just about everything. It's like your state sales tax, and it can be up to 15% in our provinces in the east, to 5% in Alberta which doesn't have a PST. They only pay the Federal part called the GST there. Unless stated, prices on the stickers on the merchandise up here do not include sales taxes, so be aware.
Typically food from grocery stores isn't taxed up here, same as in the US. However, if it's junk food, or you buy it in a restaurant, then it usually is taxed with that HST/sales tax thing.
If you compare prices in Canada to prices in the US, and do the math to convert the money back and forth, we often get less and pay more for just about everything up here.
If you exchange your US dollars for C$ up here, be aware that most Canadian financial institutions charge a foreign currency conversion/handling fee of around 2.5%. It gets blended into the exchange rate when they process your money. If possible, I would go to your local US bank and inquire about buying Canadian cash from them, as you might get a better currency conversion fee there, or they might not charge one at all. I'm not sure how US banks order and exchange foreign currencies, but I think there are some that don't charge that hidden 2.5% like our banks do up here.