I think price is based upon import/export taxes in general - Vogue Nippon is most expensive - this is mainly because of its size, it's bigger than I think all other Vogues, in height/length, even if its 1cm or so, and also the speed in which it arrives abroad - something like 1 to 2 weeks and its already here.
Vogue Australia is cheapest because the magazine is nearly two/three months behind schedule - which means it uses the cheapest shipping method, therefore the taxes are lower. If you notice Vogue Germany and Russia (now two of the next most expensive) both arrive very quickly after being released in the origin country.
Import/export taxes rise every so often depending on inflation/politics/etc so thats normally the main reason for a price hike. I don't understand why theres such a quick rise in US Vogue though, it only increased the price a month or so ago.