Overall generic drugs in the US are indeed cheaper than in Canada, but that is not the case if you don't have insurance coverage. Without that, it might be cheaper for some to order the Canadian generic if they can't afford insurance.
The other factor is not price, but availability. Some generic are in limited supply or are outright not available in the US.
Generics need to be more carefully sourced if outside the U.S. I prefer brand names from reputable manufacturing areas (Singpore, Germany, etc.), and can get them for close to the price for generics, often starting research at PharmacyChecker.com
The other factor is not price, but availability. Some generic are in limited supply or are outright not available in the US.