Whenever I talk with some of the American friends I have, they never fail to be amazed by how much Canadians pay for their data. Since there is so much competition in America, nearly every single carrier offers an unlimited data plan for a reasonable price due to the amount of competition there is.
In Canada, the two cell phone giants that cover the majority of the market are Bell and Rogers. Since there is little competition from the other companies, they're free to play around with their prices as they please.
Rogers is going to be raising the price of data overage from 5$/100MB to 7$, following suit of Bell who did so in April. These price hikes come after the news that the CRTC, the government regulatory body on telecommunications capped the amount people can pay for data overages at 50$.
Telus has announced that they would keep their prices at 5$ and Shaw does not charge overage at all instead hampers data speed when you exceed your limit.