Know. Your. Audience.
Where are these commercial being run? America. Now, I bet they'd crash and burn in Western Europe and I'm virtually certain they'd crash in Japan, but in America, they work.
Also, it should be pointed out that it is not just that they are cheap, but that they "do everything I want" (which is all the Apple could do) and that they are much cheaper, not just a little cheaper. "Does everything I want" for $2000, or "Does everything I want" for $900 is not a bad sales pitch.
(Incidentally, I'm not trying to be anti-American, nor do I think this is anti-American per se. Being cheap is neither good nor bad; it has advantages, it has disadvantages. Being able to be sold something "premium" just because it's "premium" isn't necessarily a good place to be, either. It is simply that American culture will take cheap over almost any other attribute.)