The boxset is only really good for new _collectors_ nothing in the boxset is great for gamers as the models are all meh options to game with. So if you are a new collector in the US, the price isn't too bad as there is a bunch of savings. Old collectors/games, probably already have most of the kits and probably don't need any more of those other units.
Sooo normally the price difference between US and AUS prices is 30-40%, but this boxset is 70% more, I think a lot of local stores will miss out on sales with such a significant price difference.