With major indices such as the S&P 500 back to record highs, stocks are arguably becoming more expensive than before the coronavirus market crash. Indeed, the recent market sell-off is making investors take a hard look at the value of their holdings, causing them to wonder if they overpaid for certain stocks by buying at the peak. 

Furthermore, the concern about overvaluation and over-speculation has led many to ditch high-growth companies and go bargain hunting. Three of the cheapest stocks right now are an ad-tech company, a healthcare conglomerate, and a pharmacy giant. Let's take a look at why they are ideal choices for value investors. 

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1. Criteo

One of the cheapest stocks in the entire tech sector is French ad-tech company Criteo (CRTO 1.76%). The company is engaged in the business of ad retargeting, which is delivering advertisements to consumers who are unsure about making a purchase on retail websites in an attempt to persuade them back into buying. The practice is not without controversy, as retargeters rely on retrieving a consumer's cookies across multiple websites to deduce possible shopping behavior, leading to privacy concerns. 

Recently, Google announced it would disable advertisers from accessing third-party cookies on its Chrome browser over the next two years, similar to Firefox and Safari. As a result, Criteo's revenue and adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) plummeted by 18% and 30%, respectively, in the second quarter of 2020 compared to the first quarter of 2020. 

There is, however, a light at the end of the tunnel. Currently, Criteo is working on rebranding itself in designing integrated media platforms for e-commerce websites, featuring its AI traffic analytic engine to optimize revenue. About 20% of the company's sales now come from this new venture. 

Remember, Criteo's core business is still generating $180 million in net revenue and $39 million in adjusted EBITDA. The company's market cap is only $750 million. In other words, Criteo is trading for as little as 10 times price-to-earnings.

At the end of the day, the company is still profitable on a free cash flow basis, and management expects a turnaround by the end of 2021 as the company begins to shift away from retargeting rapidly. If investors are looking for a cheap tech stock that has the potential to reinvent itself quickly, Criteo is not a bad option. 

2. Bayer 

Bayer (BAYR.Y -2.06%) is a healthcare conglomerate with operations in crop science, global pharmaceutical, and consumer health. In the second quarter of 2020, the company's sales saw a 3% year-over-year decrease to 10 billion euros due to patients deferring elective treatments in the wake of the coronavirus pandemic. 

Despite this setback, the company still generated more than 1.4 billion euros in free cash flow to maintain its impressive dividend yield of 4.5%. Bayer is trading for just 15 times earnings and 1.4 times sales. 

For the full year, Bayer expects to bring in 43 billion euros in revenue and 6.60 euros in earnings per share, both representing slight increases from last year. Each share of Bayer's American Depository Receipt (ADR) represents one-quarter of Bayer's ordinary shares. Considering Bayer's valuation is dirt cheap, and the fact that the company has nine drug candidates in phase 3 clinical trials, now is a good time for healthcare investors to buy some shares. 

3. CVS Health

CVS Health (CVS -0.57%), one of the nation's biggest pharmacy chains and a large health insurer, is encountering significant tailwinds in its core business due to the impact of COVID-19. In the second quarter of 2020, the company's revenue and earnings per share increased by 3% and 51.7% to $65.34 billion and $2.26, respectively. That's a staggering amount of increase in net income for a large-cap company.

As it turns out, CVS's retail pharmacy business only grew slightly compared to last year. The center of attention instead falls on the company's health insurance business. As mentioned previously with Bayer, fears of COVID-19 led Americans to largely defer elective procedures during the quarter, leading to a big win for health insurers. For the three months, CVS paid out 70% of the health insurance premiums it collected in reimbursements instead of the 84% it paid out in Q2 2019. 

Simultaneously, the number of members enrolled in health insurance plans grew from 22.8 million last year to 23.6 million as of June 30. CVS also witnessed a roughly 5% increase in pharmacy sales in July. The company is trading for just 9.5 times price-to-earnings and 0.3 times price-to-sales. 

CVS is also improving in terms of financial health. By 2022, the company's financial leverage, measured by net debt-to-EBITDA, will likely fall below three times. The company also has $13 billion in cash, investments, and access to credit facilities to cushion any material business headwinds in the short term. 

For the entirety of fiscal 2020, CVS expects it will generate up to $11.5 billion in cash flow from operations, which is more than enough to cover the $660 million it pays out in dividends per quarter. The stock currently has a yield of 3.35%.