History says that if you buy high-quality businesses and hang onto them for long periods of time, you'll have a very good chance of making money. After all, the S&P 500 hasn't had a rolling 20-year period between 1919 and 2020 where an investor would have lost money, inclusive of dividends paid.

However, it's psychologically tougher to convince ourselves to put money to work in the market when it's regularly hitting new all-time highs. We want to feel like we're getting a good price when we buy equities, but that can be tough to accomplish when the benchmark S&P 500 is breaking records on a near-weekly basis.

But I have good news: Discounts on great stocks are available, if you're willing to do a bit of digging.

There are currently three game-changing stocks at the forefront of innovation in their respective industries that are all down at least 40% from their respective 52-week (and all-time) highs. Best of all, they look like serious bargains relative to where they stood just a few months ago.

A digital LED sign that reads, Super Sale.

Image source: Getty Images.

Teladoc Health: 41% below its 52-week high

Among healthcare stocks, few, if any, were aided more by the pandemic in 2020 than telemedicine-services provider Teladoc Health (TDOC -3.94%). Yet in spite of its huge year, Teladoc's share price has pulled back approximately 41% from its all-time and 52-week high, set in mid-February. That's a bargain ripe for the picking.

Last year, with physicians wanting to keep at-risk and potentially infected patients out of their offices, demand for virtual visits soared. Teladoc handled 156% more virtual visits in 2020 than it did in the preceding year.

Though there have been some concerns as to what would happen to Teladoc once the pandemic ended, the company's growth trajectory and healthcare-benefit profile projects well for its future. Telehealth is considerably more convenient for patients and can allow doctors to more easily touch base with chronically ill patients.

It's also a big win for insurance companies. Virtual visits are typically billed at a lower rate than office visits, and more frequent consultations with chronically ill patients might lead to better long-term outcomes (i.e., lower long-term expenses). These benefits are precisely why Teladoc's sales grew by an annual average rate of 74% between 2012 and 2019.

Another reason you're going to want to own Teladoc is its recent acquisition of applied health-signals company Livongo Health. Livongo utilizes patient data and artificial intelligence to send its members tips and nudges that are designed to help them lead healthier lives. Once again, we're talking about improving patient outcomes, which is something health insurers are going to get behind.

Livongo has already courted more than 500,000 diabetes members and has plans to include patients with hypertension and weight-management issues. In other words, its patient pool encompasses a large percentage of the U.S. population.

Look for Teladoc Health to potentially quintuple its annual sales by mid-decade to north of $5.6 billion, according to Wall Street's consensus estimate.

An engineer plugging wires into the back of a data center server tower.

Image source: Getty Images.

Fastly: 50% below its 52-week high

If you like sifting for discounts, you're going to love edge cloud-services provider Fastly (FSLY -1.82%). Since peaking at $136.50 in mid-October, shares of Fastly have given back half their value. That discount makes little sense for long-term minded investors.

Like Teladoc, Fastly was uniquely positioned to benefit from the pandemic. The company is primarily responsible for expediting the delivery of content, including images, video, and streaming, to end users in a secure manner. With people stuck in their homes during the pandemic, consumers and workers went online and into the cloud. This meant a big uptick in demand for content-delivery network services.

Even though Fastly's new customer growth slowed a bit in the fourth quarter and it forecast a wider-than-anticipated loss in 2021 as it reinvests in growth initiatives and hires more people, the proof is in the pudding that its customers approve of its services. Last year, Fastly had a revenue-retention rate of 99% and a dollar-based net expansion rate (DBNER) of 147% and 143%, respectively, in the third and fourth quarters. In plainer English, DNBER tells us that existing clients spent a respective 47% and 43% more in Q3 2020 and Q4 2020, respectively, than they did in the year-ago quarters (Q3 2019 and Q4 2019). 

Just as impressive, we saw Fastly overcome an operational hurdle in the third quarter. During the first half of 2020, popular social media platform TikTok accounted for an eighth of total sales. But with TikTok parent ByteDance quarreling with the Trump administration stateside, it pulled most of its traffic from Fastly's network.

What looked devastating proved ultimately harmless. Full-year sales grew by 45% to $291 million and adjusted gross margin expanded 430 basis points to 60.9%.

Fastly's business is set up perfectly to take advantage of increased content-delivery demand over time. This high-margin, usage-based model should make Fastly and its investors rich.

A person using a laptop to conduct a web conference with four other people.

Image source: Getty Images.

Zoom Video Communications: 43% below its 52-week high

A final game-changing stock that's been substantially discounted in recent months is web-conferencing giant Zoom Video Communications (ZM -3.04%). Since peaking at almost $589 a share on Oct. 19, 2020, the company has since given back 43% of its value through this past weekend.

Not to sound like a broken record, but Zoom Video was also a major beneficiary of the pandemic. When the coronavirus shut down traditional offices, workplaces shifted to people's homes. To keep projects going, businesses big and small began turning to web conferencing. This is why Zoom reported $2.65 billion in sales last year, which represented a 326% increase from the prior-year period.

One of the big reasons Zoom has been such a success is the company's freemium lure. Zoom offers a free trial of its cloud-based conferencing solutions that's proved highly effective at getting businesses to subscribe. In particular, the company's conferencing solutions have really resonated with small-and-medium-sized businesses. Last year, customers contributing at least $100,000 in trailing-12-month revenue rose 156%. But the number of customers with at least 10 employees surged 470% to 467,100

And have I mentioned the sheer dominance? According to Datanyze, Zoom controls just shy of 40% of the U.S. web-conferencing market. That's essentially double its next-closest competitor, and makes it the logical choice for most businesses. 

The efficiencies that Zoom's platform provides businesses makes it highly unlikely that we're going to see its growth slow dramatically in the coming years. If anything, Zoom's cash flow windfall gives it the incentive to expand its services beyond web conferencing.

Like Teladoc, Zoom looks to be on pace to roughly quintuple its sales over the next five years.