Not long ago, the idea of Apple (AAPL) shares topping $300 seemed unthinkable. Yet here we are, watching the stock approach $350 on a clear march to $400.

Now The Wall Street Journal is discussing the possibility of Apple soaring to $1,000 a share. Impossible? Perhaps. What would it take for that to happen?

Brett Arends admits that Apple has made him "look like a total idiot." He dared to question whether Apple's stock could keep up its amazing momentum. And since then, the growth rate of the stock has ratcheted up to an annualized 67%.  

Now Arends and other critics are at least opening up to the possibility of a $1,000 stock price. Apple impresses the market every quarter with jaw-dropping earnings, and its net income has been on a tear. The iPhone has expanded to Verizon Communications (VZ), a new iPad is expected within months, and the MacBook and desktop business is dependably solid.

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If Apple stock keeps it up, Arends calculates, it will hit $500 in October and $1,000 by February 2013. He says $500 call options, good until January 2013, are $20 a share at this point. For Apple to hit $1,000, its market value would have to reach around $900 billion (assuming there aren't big changes to the outstanding share total of 920 million), Arends writes.

Apple trades at about 17 times expected earnings. If that remains the same, Apple would need to hit $53 billion in annual profit to reach a market value of $900 billion.

So there's the magic number: $53 billion. Last year Apple's profit was only $14 billion.

On the revenue side, Arends calculates that Apple would need about $240 billion in revenue to get a profit of $53 billion. That would mean significant sales increases just about everywhere: Europe, Japan, China, India, Brazil and of course the United States.

Is this even possible? "You make the call," Arends writes.

This whole conversation seems fairly ridiculous. Arends assumes too many things will stay constant in his calculations (including P/E, share float and internal costs), and of course they won't. His back-of-the-envelope​ numbers are too simple for a complex international sales operation involving emerging markets.

But he's now put it out there: Apple at $1,000.