Justify buying AAPL at 400+: Ok, that's easy. And I'll do it in just one word- China.
The last two days should have proved to everyone that the Chinese market is certainly the most enticing, and relatively unchartered, market for Apple. Yes, we know: rapidly expanding GDP per capita, massive middle class growth, increasingly opening up their telecommunications sectors, and blah blah blah.
What is more important is the telling signs from the last week of news about Apple in China, for no matter what Apple does, the Chinese still insanely crave their products.