Very simple: There is growth (or not) in Apple's business, and there is growth (or not) in Apple's share price. Apple's share price is based on Apple's profits today, plus a prediction how Apple's profits will grow over the years. So the AAPL share price is higher than Apple's business today would warrant, because there is a prediction of growth.
Let's say the share price is based on the guess "Apple will grow 25% for the next four years and then stop growing". So Apple is expected to grow for four years. For shareholders, the question is: What will people predict four years from now? If in 2015 every analyst says "we were absolutely right, Apple grew 25% for four years, and now we expect them to stand still" then the share price will be unchanged from today's. If they predict "Apple will grow one more year and then stand still" then the share price would grow by these 25%. If they have the same prediction "Apple will grow another four years" that they have today, then the share price would go up quite wildly.
Ha ha ha! thank you for the great explanation. Im afraid I discredited my knowledge in this regard a little too much