Just so. Wall Street has an amazing habit of running growth tech companies up to insane prices. Look at the history of Cisco for a graphic example. The current stock prices of the darlings of the Internet advertising boom (Facebook, Twitter, Google, and the like) reflect the view that their historical growth rate will be sustained for a decade or more to come, and that's not just unlikely, it's impossible. If you extrapolate their future earnings from their current prices, Wall Street expects each one of them to soak up the entire advertising spend of the entire planet .... which seems unlikely, given that there are several of these giant tech darlings and only one planet. Total world advertising spend (all media, print, web, outdoor, radio, TV, everything) is essentially static: it hasn't changed much in decades other than in (approximate) line with overall economic growth.
Now you might argue that one of them will end up with earnings on that scale. It's not impossible after all. But they can't all have 100% of the same cake!
Apple, like most (all?) of the other tech darlings will do a Cisco. The company will remain successful, will still generate huge profits, might even continue to grow a bit .... but not at a pace anything like fast enough to justifty the ridiculous share price. In the medium to long term, going short on all of the giant tech darlings (Facebook, Apple, Microsoft, and etc.) is a can't lose strategy. You might (might!) be wrong with one of them, even two of them, but you'll still be a mile ahead.
(Least likely to decline: probably Amazon, followed by Google. Twitter is walking dead; Facebook has hit the wall, Microsoft .. less said the better; Apple is well past its peak.)