Buy low and sell high sounds easier than it is, but when premium stocks are trading below their true value, it's hard to miss.

Berkshire Hathaway CEO Warren Buffett built his $60 billion-plus fortune by buying high-quality businesses at discounts. The Oracle of Omaha summed up his love for bargains with this quote: "Whether we're talking about socks or stocks, I like buying quality merchandise when it is marked down."

Today we'll look at four dividend-paying businesses that are industry leaders with strong competitive advantages. Three of them are in the elite group of 50 stocks known as Dividend Aristocrats, stocks that have 25 or more years of consecutive dividend increases. The other is one of the largest corporations in the world.

The market has unfairly punished all of these businesses. You can take advantage of current discounts by loading up on these high-quality businesses trading at bargain prices.

1. Walmart (WMT - Get Report)

Any article discussing industry-leading companies naturally needs to include Wal-Mart Stores, whose Walmart discount locations make it the biggest retailer in the world.

Walmart is a behemoth in retail and generates about $480 billion in annual revenue. And while it has struggled in recent years, it may still have growth ahead of it.

Walmart's problems are well documented; the company's public image has suffered because of the way it treats its employees and the condition of its stores. Sales and earnings declined in fiscal 2016. Walmart recorded $4.57 in diluted earnings per share in fiscal 2016, which was an 8% year-over-year drop. One of the key reasons for the earnings decline was unfavorable foreign exchange rates, and the stronger dollar is expected to reduce sales by $12 billion this fiscal year alone.

Fortunately, Walmart could still have growth opportunities ahead of it. There are two major catalysts investors can look forward to: e-commerce and small-format stores. These are leading the company back to growth. Last quarter, the small-store Neighborhood Markets banner increased sales 8%; e-commerce sales were up 12% last fiscal year.

Consumers are demanding greater shopping flexibility, which means Walmart's renewed focus on digital sales and smaller Walmart stores is likely to pay off. In the meantime, investors are paid well to wait. Walmart is a Dividend Aristocrat, having raised its dividend for 43 years in a row. The company is also recession resistant and makes an excellent choice for bear markets.

Walmart stock currently offers a nearly 3% yield based on its current share price. That is significantly above the S&P 500 average dividend yield of 2%.

And, Walmart stock is on sale. Shares trade for a price-to-earnings ratio of 15, which is less than the P/E of the S&P 500, currently at 23.7. The cheap valuation offers a margin of safety against downside risk, as does its high dividend.

2. Archer-Daniels Midland (ADM - Get Report)

Archer-Daniels-Midland clearly is being negatively affected by the downturn in prices of agriculture commodities.

The stock trades for a price-to-earnings multiple of less than 13, which is well below the S&P 500's P/E.

Declining prices for commodities including soybeans have weighed on Archer-Daniels Midland's earnings. Also contributing to its weakening profits is the strengthening dollar and rising global supply, which have reduced exports and margins.

Because of these factors, Archer-Daniels Midland's net sales and adjusted EPS declined 17% and 13%, respectively, last year.

Things haven't gotten much better in 2016. Its adjusted earnings per share fell 49% in the first quarter, driven by declining performance in its agriculture trading business and lower U.S. exports.

One positive development from the first quarter was that the operating profit in the corn-processing business increased 1.5%.

The company has remained profitable through the downturn, and it has a long track record of uninterrupted dividend payments.

Archer-Daniels-Midland recently declared its 338th consecutive quarterly dividend payment, a record of 84 years of uninterrupted dividends. It raised its dividend by 7% last year, and over the past five years, it has increased its dividend by 13% compounded annually.

The current dividend yield is an attractive 3.1%.

Archer-Daniels Midland has employed a significant cost-cutting program to keep the company profitable, which will allow it to continue returning cash through dividends and share buybacks. It achieved almost $50 million of cost savings in the first quarter and plans to reduce company-wide costs by $275 million by the end of 2016.

Earnings should be further boosted by its aggressive share repurchase program. Archer-Daniels Midland repurchased about $300 million of its own stock in the first quarter.

Investors should feel confident that the dividend is secure, even in a difficult climate. The dividend represents just 40% of Archer-Daniels Midland's 2015 earnings per share.

3. ExxonMobil (XOM - Get Report)

Exxon Mobil has suffered a lot of bad news over the past year, driven by the collapse in oil prices. In a prolonged period of low oil prices, even a best-in-breed company like Exxon Mobil isn't immune. The company recently lost its triple-A credit rating. 

The good news is that ExxonMobil is still profitable and continues to reward shareholders with increasing dividends.

Exxon Mobil recently increased its dividend by 2%. The new dividend level represents a 3.4% dividend yield based on its current share price.

Exxon Mobil has paid uninterrupted dividends for more than 100 years. This dividend increase makes 34 years in a row of consecutive annual payout increases, which qualifies Exxon Mobil as a Dividend Aristocrat. It is also the largest of the six oil and gas super majors.

In comparison with its industry peers, its fundamentals have held up better than most. ExxonMobil still earned $16.15 billion in profit last year.

ExxonMobil generated a 7.9% return on average capital employed in 2015, proving that it is still an excellent steward of shareholder capital. Exxon Mobil has accomplished consistent profitability and positive returns on capital by focusing on efficiency and slashing costs to the bone.

The company cut its stock buyback program by $9 billion last year. It also cut capital and exploratory spending by 19% in 2015.

Another factor helping Exxon Mobil's profits stay afloat is its huge refining business. Exxon Mobil's downstream earnings more than doubled last year, to $6.5 billion.

Overall, adjusted EPS fell 63% year over year in the first quarter, but again, the company remained profitable. First-quarter profits totaled $1.8 billion, thanks to a 33% reduction in capital spending.

While the 2% dividend increase isn't much to get excited about, considering how many energy companies have cut dividends in the past year, investors should feel great about getting any increase at all.

And, ExxonMobil stock is cheap. Shares trade for an enterprise value-to-EBITDA ratio of 13, which is fairly cheap considering that analysts expect adjusted EPS to increase a robust 67% in 2017.

4. Apple (AAPL - Get Report)

Apple has seen a slowdown in device sales this year, and investors have rushed for the exits. The stock is down 28% in the past year.

Investors seem panicked that Apple's results last quarter were discouraging. Apple recorded adjusted EPS of $1.90 on $50.56 billion of revenue but missed analyst expectations on both measures.

Sales fell across all of Apple's geographic markets except Japan. Particularly concerning are deteriorating business conditions in China, where sales fell 26% last quarter.

Sales fell across Apple's three most important devices: the iPhone, iPad and Mac. iPhone sales fell 18% from the same quarter in 2015, which is a significant concern because the iPhone represents 65% of Apple's total revenue. Overall, sales were down 13% for the quarter.

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This selling pressure has pushed Apple's valuation down to a very cheap level. The stock trades at a P/E of just 10. The market clearly does not have high expectations for Apple moving forward.

But what investors are missing is that even though its growth rate is slowing, Apple still generates huge amounts of free cash flow, including $33 billion of free cash flow over just the first half of the fiscal year.

Apple ended last quarter with $232 billion in cash, short-term investments, and long-term marketable securities on its balance sheet.

Such huge amounts of cash allow Apple to continue rewarding shareholders with increasing cash returns, including dividends and stock buybacks.

Apple recently announced a 10% dividend increase and added $35 billion to its stock buyback program. The dividend currently provides a 2.5% yield, which is above the S&P 500 average.

In all, the company will raise its total shareholder capital allocation by $50 billion. Apple now expects to spend a total of $250 billion under its current capital return program.

Going forward, Apple will release the iPhone 7 by the end of the year, which should be a strong growth catalyst. Further penetration in China, along with entry into new markets like India, could reignite Apple's growth soon.

As a result, the stock may not be this cheap for long.

This article is commentary by an independent contributor. At the time of publication, the author held shares of WMT, ADM, and XOM.