We’ve been following Andy Zaky’s posts on Bullish Cross since 2007 and have found, as he likes to remind readers, that he’s one of the best independent analysts following Apple (AAPL). His estimates of Apple’s quarterly earnings are uncannily accurate. In the years we’ve been tracking them, they’ve never failed to beat those issued by the Wall Street professionals.

Yet only three times in the past five years has he recommended that his readers buy Apple shares:

• July 2006 at $50-$54: 6-month $100 price target
• November 16, 2008 at $88.14: 24-month $230 price target
• August 11, 2010 at $250.19: 18-month $400 price target

Two of those recommendations have paid off richly, and the third still has another eight months to do so.

On Friday, Zaky issued his fourth “buy” on Apple:

• June 17, 2011 at $320.00: 18-month $500 price target

“At $325 a share,” he wrote on Seeking Alpha, “Apple currently trades at 8.13 times our 2012 earnings estimates.”

“The current Wall Street consensus is showing Apple trading at 11 times next year’s earnings,” he adds with characteristic bravado. “The consensus is wrong, we’re right, and therein lies our advantage over the market.”

The market, however, doesn’t seem to give a damn.

Apple’s shares continued their post-WWDC downward spiral despite Zaky’s buy signal, dropping $4.90 (1.5%) Friday to close at $320.26, and falling another $9.76 (3.1%) in early trading Monday.

Zaky is undaunted:

“For those who are holding the stock here at $320 and have a long-term horizon, don’t fall victim to the market’s volatility. As Art Cashin would say, ‘the market wants to make fools of as many people as it possibly can.’ Those buying the stock today with a two-year horizon will make 56.3% on their money. The market will do what it can to shake everyone out of their positions. Keeping a level head during this obvious shakeout attempt will be met with significant rewards in 2012.”

You can read his full post here.

Note: Zaky is an occasional contributor to Fortune.com, which publishes this blog.