1) Toronto is highly populated.
2) Alot of people in Toronto are wealthy.
3) Only one NFL game per year. Might at well charge a premium.
Toronto is a gorgeous city, but the football atmosphere is terrible. I live close to Toronto, and I know alot more Pats/Steelers/etc. fans than I do Bills fans, so there are alot of bandwagon fans living in the area.
With that being said, there are some intense Bills fans in Canada (myself included) but I think we all prefer traveling to the Ralph. The Rogers centre is a joke.