Perhaps the most succinct commentary on Leonid Kanopka’s naive claim that Apple (AAPL) is a “bubble ready to burst” (see “A few fries short of a Happy Meal“) was Nicu Mihalache’s plaintive response: “Do you know what P/E is?”

The price-to-earnings ratio, as every trader knows, is the simplest way to gauge how the market values a company. A high P/E — like the nearly 50 times earnings investors were paying for Apple four years ago — is a signal that the market has high hopes for a company. A low P/E — like the current 10.05 forward earnings ratio — is a vote of no confidence.

There are more sophisticated ways to value a company. Asymco’s Horace Dediu, who produced the chart above, favors P/E/tG (price to earnings to trailing growth). But his P/E chart, which shows Apple trading in a band between 35 and 45 times earnings between 2006 and most of 2008 and between 15 and 25 times earnings since 2008, tells you most of you need to know. In a piece posted Thursday entitled The Thermodynamics of  Apple’s Share Price Dediu writes:

“Note that the price has dropped outside the current band for the first time since the great recession. It is still below 15xE today. Perhaps a new band is forming.”

What’s going on?

Building on a report Andy Zaky issued Monday on Bullish Cross showing that Apple is now the most undervalued large cap stock on the S&P 500, Reuters blogger Felix Salmon surveyed the Apple nay-sayers’ arguments and came up with 8 reasons Apple’s shares are so cheap. To his list, which runs the gamut from “it’s run out of buyers” to “technical analysis astrology,” I would add two more:

One from Dediu who summarized his takeaway from a series of meetings with buy side analysts like this:

“The consensus is that the value of future, unknown products is zero. Not only that but the probability that there will be any products at all is equally zero. Not only that but whatever Apple does to create new products is not perceptibly valuable.” (See “Is Innovation Valuable?”)

The other comes from reader Jim Neal in an e-mail entitled “Why I’m happy with Apple’s P/E”:

“If one really needs an explanation for why Apple isn’t running like a speedboat in these choppy waters, just remember that regardless of how much money it is making now, the business model of making just a few great products is never going to be seen as being terribly safe, so the more money you make, the more worried some people will be. Apple’s product line just isn’t diversified enough from the typical investor’s perspective.  They see RIMM and CROC and other companies that have crashed and burned.  To them there’s nothing special about AAPL, or if there was, the company lost it this year. That I don’t agree with that assessment really, is irrelevant. Tim Cook knows what he’s doing.  Mr. Ive does too.  Iger’s no slouch either.  But until a few new rabbits are pulled out of the hat, investors will remain on edge.”