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What a difference a year can make.
Though the company's stock has taken a breather in the past few days, it has experienced a rapid run-up in recent weeks that's left investors scrambling—and skeptics scratching their heads.
One year ago, Tesla stock was puttering along at about $35 a share. This week, it briefly hit a record high of $265 a share before pulling back to a still lofty impressive price near $250 a share. The numbers are daunting any way you look at them. Investors now value Tesla at more than $30 billion, as its stock trades at more than 1,000 times earnings.
(Read more: Tesla sets huge note offering)
And that's if you're willing to accept the company's assertions that it earned $46 million in the fourth quarter. Using the more generally accepted accounting practices most companies hold to, Tesla was actually $16 million in the hole.
So what's allowing the automaker to fly so high, and can it maintain that momentum? That, quite literally, is a $30 billion question.
Investors "are playing an expectation game," betting on rumors and whispers that things will look better next quarter, said Joe Phillippi, president of AutoTrends Consulting.
"These are momentum players," he said. "God forbid Tesla misses a number or has a problem with a [future product] launch."
Tesla's Model S sedan, which is the only car the company has on the market, has won rave reviews. Earlier this week, Consumer Reports named the car its top overall pick among all vehicles.
But with sales averaging at around 5,000 vehicles a quarter, the real test will come when Tesla launches the Model X SUV and the Model E, which are still in development.
Another big question surrounds the safety of its battery pack. Three well-reported fires involving the Model S late last year initially caused the stock to plunge. But another fire this month caused only a momentary blip in Tesla's climb.
(Read more: Tesla to Texas: How do you like us now?)
The automaker continues to wait for word on an investigation by the National Highway Traffic Safety Administration. Getting the all-clear could put add even more momentum to Tesla shares. On the other hand, were the NHTSA to conclude there's a safety-related defect and order a recall—particularly one involving the basic chemistry of the Tesla batteries—the stock could come unplugged.
Another potential mover could come from Apple. Following recent reports that Musk met last year with the head of that company's mergers and acquisitions department, Tesla's stock has surged more than sevenfold. Some reports suggest that the two companies might be looking for ways to work together on future projects.
And after hinting last week that Tesla was exploring the idea of building a "gigafactory," Musk dropped yet another bombshell this week: A report initially suggested that Tesla and its battery supplier, Panasonic, were looking to invest $1 billion in the project, but the real number is going to be closer to $4 or $5 billion.
(Read more: Tesla soars, Ford falls in 'Consumer Reports')
A few months back, Tesla warned it might not have enough batteries to meet its future needs. If the gigafactory project pans out, it could provide Tesla with enough ammo to become a mass manufacturer. Better yet, it could yield a sharp reduction in the cost of lithium ion batteries—the single biggest cost in building the Model S, and pretty much any other electric vehicle—while yielding improved range and vehicle performance.
Those are big "ifs" but far from the only ones about Tesla. Nonetheless, a new report from Morgan Stanley projects the maker's stock could top $320. Other analysts have been far less ebullient, with some looking at figures closer to $80 a share. But so far, the bulls are running the show. The question remains whether anything might come along to short-circuit Tesla's run-up.
—By CNBC Contributor Paul A. Eisenstein. Follow him on Twitteror at thedetroitbureau.com.
Correction: An earlier version of this story said Tesla sells around 4,000 vehicles a quarter.