As of this past weekend, there were fewer than 120 companies whose valuation topped $100 billion. Call me old-school, but I've always considered a market cap in excess of $100 billion to be a megacap stock (today, some folks believe in a megacap cutoff of $200 billion).

Historically, companies that surpass a $100 billion market cap are slow-growing, but they're often profitable, time-tested, and offer modest long-term appreciation. However, the latter may not be the case for a trio of megacap stocks.

Of the nearly 120 companies with at least a $100 billion market cap, only three have a high-water Wall Street price target that implies a doubling in their respective share prices. Can these megacap stocks actually double? Let's take a closer look.

A neat stack of one hundred dollar bills, a calculator, and a pen, laid atop a financial newspaper.

Image source: Getty Images.

Tesla Motors: Implied upside of 129%

Perhaps unsurprisingly, auto stock Tesla Motors (TSLA 0.79%) offers the highest implied upside, based on the beefiest Wall Street price target -- $1,471 a share -- as of this past weekend. If this price target came to fruition, we'd be talking about a 129% increase in Tesla's stock. It's also worth mentioning that ARK invest CEO and Chief Investment Officer Cathie Wood believes Tesla can hit $3,000 a share by mid-decade. 

The obvious reason for bullishness has to do with the epic multi-decade vehicle replacement cycle that'll see people and businesses switching to electric vehicles (EV) and other forms of alternative energy-powered transportation. Tesla had a first-mover advantage in the U.S., and it's building a name for itself in China, which is the largest auto market in the world. By 2035, the Society of Automotive Engineers of China estimates that half of all new vehicles sold in China will be powered by alternative energy.

Another reason some Wall Street analysts have rallied around Tesla is the company's clear-cut competitive advantages. For example, Tesla's batteries have higher capacity, more power, and better range than the batteries being developed by its peers. The introduction of the Model 3 also brought the price of entry-level EV ownership down considerably.

But Tesla is also a highly polarizing stock, with a low price target from Wall Street of just $67. That's because there's a mountain of competition brewing in the EV space domestically and abroad. General Motors (GM -0.10%) plans to spend $35 billion on EVs and autonomous innovation through mid-decade.  Meanwhile, Ford Motor Company (F -0.84%) is planning to spend $30 billion through 2025 on EVs. GM and Ford will each be launching 30 new electric vehicles globally within five years. 

An even bigger concern might just be Tesla's inability to generate a profit from selling EVs. Although it's been reporting adjusted quarterly profits for more than a year, Tesla's "profitability" has hinged on it selling renewable energy credits to other automakers or selling its digital assets (Bitcoin) for a profit. It's hard to envision Tesla being worth $1.4 trillion without even demonstrating to Wall Street that it can generate a recurring profit from selling EVs.

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Image source: Getty Images. Implied upside of 101%

Wall Street is also expecting big things from China's second-largest online retailer, (JD -2.02%). Though the consensus of all analysts is that JD offers a hearty 43% upside, one analyst foresees the company making a currency-converted run at close to $105 a share. This implies potential gains of 101% for the e-commerce giant.

Wall Street's fascination with JD has to do with its similarities to and its (pardon the pun) prime location (i.e., at the heart of China's rapidly growing economy). Though the company does, in certain instances, act as a third-party marketplace, it's primarily a direct retailer of goods to online shoppers and maintains its own inventory. Having greater control over product quality and logistics is what's helped Amazon to generate insane amounts of cash flow, and it should do the same for JD. As of the end of March, JD's annual active customer count was a stone's throw from 500 million, up 29% from the prior-year period. 

Equally exciting is the rapid growth JD is experiencing from its service operations, which encompasses things like healthcare services, cloud services, and advertising. In late April, Cloudflare announced that it would partner with JD to expand its network in China. For JD, Cloudflare's use of its cloud infrastructure will create another channel of fast-growing sales. In Q1, this service segment grew sales by a blistering 73% from the prior-year quarter. 

However, JD is far from being the only fish in the pond in the world's second-largest economy. Though being a direct retailer comes with its advantages, it's nevertheless under constant pressure from the likes of Alibaba and Pinduoduo. Even Tencent Holdings, which has been a longtime shareholder of JD, is a potential threat with its slow but steady push into mobile e-commerce.

Yet, even with increasing competition and regulatory uncertainty in China, JD offers a very realistic shot at eventually hitting Wall Street's upper echelon price target. Take note, I'm not saying JD gets there within 12 months, as is the common timeframe for Wall Street price targets. But within the next few years, $105 is a very realistic target given its 20%-plus sustainable growth rate and cloud services push.

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Image source: Getty Images.

Netflix: Implied upside of 124%

The last megacap stock that Wall Street believes has the potential to double is streaming content provider Netflix (NFLX 1.04%). The most aggressive price target on Wall Street foresees Netflix galloping to $1,154 a share, or 124% higher than where the company settled this past week.

Similar to Tesla, Wall Street's fascination with Netflix has a lot to do with the company's first-mover advantage. Folks were scratching their heads when CEO Reed Hastings decided to shift away from a highly profitable DVD-delivery business and focus his company's attention on streaming. With hindsight being 20/20, we know this was a genius move. Netflix ended June with almost 209.2 million global streaming subscribers

Netflix also has a long history of turning heads thanks to its original programming. It's released dozens of original shows and movies, many of which have turned casual subscribers into users who become hooked on the service.

But there are also a number of good reasons to believe that $1,154 isn't achievable. For instance, competition in the streaming space has been steadily picking up, with Netflix losing some of its share in the United States. In particular, Walt Disney's streaming service Disney+ took just 16 months to go from launch to more than 100 million subscribers. The timing of the pandemic certainly helped Disney+, however its ascension can't be ignored. 

Furthermore, there's uncertainty about subscriber growth in a post-pandemic world. Make no mistake about it, we're still in a global pandemic. But with vaccination rates climbing, it's a fair assumption that people are going to be spending more time outside their homes rather than in front of their televisions or laptops. This could certainly slow Netflix's subscriber growth.

A final reason for skepticism in this high-water price target is Netflix's long history of net cash outflows. It's no secret that Netflix wants to expand internationally, and it's willing to spend big to gobble up international streaming share. But it's difficult to imagine Netflix being worth close to $500 billion without any consistent positive cash flow.