I like to keep an eye on AAPL valuation.
Right now at a price of $489/share the company's market cap is $472 billion. Let's do a back of the envelope Peter Lynch style quickie on it. P/E at this price, TTM is roughly 11.3.
Now let's back out AAPL's cash pile of $130 billion (cash and very non-volatile marketable securities.) There is no debt. That gets us to a company with an adjusted market cap of $342 billion, or a cash-adjusted P/E of 8. I like to knock off a point of P/E for every percent of dividend yield for comparison purposes, so we're trading closer to a for-comparison-purposes P/E of 7 today. (The comparison is to a similar company with no cash pile, no debt and no dividend, and there are plenty of those out there, including the average S+P stock, trading at a P/E of 15.)
The historical P/E of AAPL valued by this method is closer to 12, so the market is saying AAPL is a value trap and earnings should decrease 40% short-term. I get that - sure, it's a possibility - but do you believe it? Do you believe that AAPL is now among the worst stocks trading in the S+P 500 index?
Well, if so, don't buy any AAPL at this price. Otherwise take advantage of Mr Market's bipolar swing and back up your truck.