Its not that crazy when you look into it more. Montreal to Paris is a low yielding route filled mostly with price-conscious tourists. New York to Paris has, as a percentage, substantially more business travel, which can sustain higher fares. For each route, the airline (presumably Continental) is trying to extract what it sees as the maximum price the market is willing to bear.

As another example, Des Moines to Dallas as discussed in this article. American has the only non-stop flights between those two cities, and any connection is going to add at least 2 hours to your travel time (based on a quick glance). On the other hand, nobody has a nonstop between Des Moines and Los Angeles, so American has no competitive advantage there and cannot command a huge price premium.