Why Canadian Price Variants?
In short scarcity. The value of most collectibles is driven by scarcity, the rarer an item the more it may be worth. Canadian Price Variants (CPV's) are just such an item. cpvpriceguide.com has a great article explaining this in depth, however it can be summarized as follows: for nominally 10 years (1980's) Marvel and DC sold Newsstand comics in Canada that were priced higher than the Newsstand version in the US due to the US/CAD exchange rate. These comics are identical to the US version coming off the same printer, using the same paper and inks, only the price was different.
Since the population of Canada is significantly smaller than that of the US, fewer comics with the price variant were sold. In addition since they were all Newsstand versions they were much more likely to be purchased by "readers" vs collectors who would still go to their LCS and could get direct versions. As a result the CPV's are not only scarce from a numbers perspective but also from a quality perspective. As the graphic shows it is estimated that about 80% of surviving comics in North America were direct edition, with only 2% of comics representing CPV's.
So why CPV's? Well if you had a chance to get a 9.8 Amazing Spiderman 238 (first Hobgoblin) would you prefer that yours be in the 80% category where there are over 450 CGC 9.8's or the 2% category where only 83 exist in a 9.0 or above and only 7 exist in a 9.8?