I agree with your premise. However I don't agree that it applies to AAPL (yet).
However good there growth has been (and don't get me wrong its been pretty amazing last few years) its entirely justified given their valuation metrics.
The thing is whichever way you slice it there isn't a single metric that would suggest they are overpriced. This kind of growth in a company is unprecedented and it is for that reason the share price is lagging. People are irrational, the market is irrational. My take is that people are too scared to buy because they think the price has gone to high too fast. They are still nervous. There are still plenty of skeptics.
Once the market catches up with reality, we'll see the next level of growth. It will be fast outpacing everything we've seen so far as everyone decides that maybe they are that dead cert, and that's when we'll over shoot. Probably about the same time that revenue and profit plateau (Which has to happen at some point!). Of course people will ignore this, caught in the euphoria and continue to pile in cash as its now 'a sure thing' share price will go insane.
Then its time to panic. Now, not so much.