I'm not surprised at the price difference. It's why I buy R2 copies of UK series a lot of the time -- the difference in cost is sometimes staggering. Like $23 vs. $75. Same reason too -- "speciality" titles so they charge a premium in the US.
If I had a blu-ray player, I'd probably have gotten the Canadian edition, but I don't have an HD tv or a BD player so right now, investing in blu-ray disks is kind of a waste of money. I am looking forward to seeing the film in any version.