Criterion is a lot cheaper in the US than in Canada. Here each Blu Ray are more than 30$. I prefer buying 3 movies than 1 for that price.
You can always get them online, some for even cheaper than the sale prices at B&N, but I just usually wait until these things until I actually buy them anyways. They seem to only happens a few times a year, and it gives me an excuse to go hog wild on them at one time.