"Apple is poised to enter and, in our view, dominate two new categories (the television next year and the automobile by 2020) with a combined addressable market of $2.2 trillion," Icahn wrote. "[This is] a view investors don't appear to factor into their valuation at all."
He's right. They don't.
Like Milunovich, Morgan Stanley analysts Katy Huberty and Adam Jonas declined to assign any value to Apple's auto business in a Feb. 24 report. Among the reasons why: It could take Apple as long as 10 years to build its own car, though partnerships with existing car makers could arrive sooner, they wrote. The company is also known for taking many years to pursue new markets while it tinkers with its product, as it has in TVs, they said.
Read More10 steps to understanding Apple's car plans
On top of all of this, Icahn argues that Apple is worth 18 times earnings rather than the 10 to 11 times earnings it currently commands.
"It just makes no sense that this company should be at 10 times earnings when you have a number of companies that are questionable in the S&P ," Icahn said. "They're making earnings because of low interest rates in many cases. Those earnings are going to be affected by a strong dollar in the negative way. And yet those things are selling at 18 times earnings."
Icahn has already made more than $3 billion on his 53-million-share Apple stake, which he began to build in 2013. At $130 a share, his position is worth nearly $7 billion.
But getting it to $14 billion soon will take a lot of smarts and a bit of luck—and just maybe some help from the Fed.
"It's amazing that Icahn can't be content with the move in the stock he's had," Daryanani said.
—By Tim Mullaney, special to CNBC.com