Believe it or not, the bull-market rally recently logged its eighth birthday. Since bottoming out in March 2009, the broad-market indexes have catapulted to new all-time highs. Over the trailing one-year period, the broad-based S&P 500 has galloped higher by more than 17%! Considering the average historic return of the stock market is 7% annually, inclusive of dividend reinvestment, investors are doing quite well.

Stocks on sale

However, not all stocks have been privy to the rally. In fact, Wall Street has left quite a few top stocks behind. But their underperformance relative to the S&P 500 can be your opportunity to scoop up some high-quality companies on the cheap. Here are three top stocks on sale this summer that you should strongly consider adding to your portfolio.

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Alexion Pharmaceuticals

While the broader market has pushed to new heights, shareholders of rare-disease drugmaker Alexion Pharmaceuticals (NASDAQ:ALXN) have stood by and watched their investment shrink by 6% over the trailing 12 months.

Why the underperformance? Most of the blame can be traced to lead drug Soliris' failing short in a phase 2/3 label-expansion study involving kidney transplant patients at high risk of delayed graft function (DGF), an organ transplant complication. The company has also been fighting sales fraud allegations, which led to a shake-up at CEO and CFO. In other words, Wall Street is concerned that Soliris' peak sales potential may be too lofty, and that Alexion may be led astray without a cohesive management team.

Though there's no denying that these aren't positive catalysts, both concerns could be overblown. For instance, the failure of Soliris in kidney transplant patients at high risk of DGF would have added only about $50 million annually in peak sales, and it wasn't the first time the drug failed a transplant study, according to FiercePharma. Soliris remains the most expensive drug in the world -- it can cost around a half million dollars annually -- and two of its approvals are for ultra-rare diseases for which there are virtually no competitors. It means that Alexion is likely to hang on to its pricing power for the near future, and it'll be able to use its unique focus on ultra-orphan indications to grow sales.

At the same time, there's very little concern from this Fool that the Trump administration will be successful in curbing prescription-drug inflation. Lawmakers are far too focused on the American Health Care Act and tax reform to worry about drug-price reform. What's more, without a universal health plan in place, and given that insurers rarely exclude drugs from their formularies for fear of losing members to competing networks, drug-pricing power remains in the court of companies like Alexion.

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With strong cash flow, Alexion also has the opportunity to grow its portfolio by acquisitions, as it's done with Kanuma, a treatment for lysosomal acid-lipase deficiency, which may one day have blockbuster potential.

With annual EPS expected to essentially double between 2017 and 2020 to $10.52 (based on Wall Street's consensus), and Alexion's top-line on track for 12% to 20% annual sales growth, investors should be considering this recent weakness as an opportunity to nab a fast-growing top biotech stock.

Goldcorp

Another top stock on sale this summer is large-cap gold miner Goldcorp (NYSE:GG). Over the trailing year, Goldcorp stock has lost 25% of its value, meaning a more than 40-percentage-point underperformance to the broader market.

Goldcorp's issues primarily relate to recent struggles for physical gold. Gold prices peaked last summer at north of $1,360 an ounce but closed recently at a little more than $1,240 an ounce. Lower realized prices mean lower margins for gold miners. Likewise, the Federal Reserve's having raised the federal funds target rate by 25 basis points on three occasions in roughly six months bodes poorly for physical gold. It makes interest-bearing, safe assets more attractive, and gold, which has no yield, less attractive. Nonetheless, this Fool sees value.

Though higher interest rates are a clear negative for spot gold prices, higher inflation rates (which typically accompany a growing economy), constrained precious-metal supply, growing gold demand, and clear uncertainty tied to the Trump presidency and Britain's impending exit from the European Union, are all reasons to believe the lustrous yellow metal has higher spot prices in its future.

Two gold bars stacked next to each other.

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More specific to Goldcorp, the company has managed to keep its all-in sustaining costs (AISC) among the lowest in the industry. Goldcorp is able to use the byproducts it mines to help offset its gold-mining costs, which in the first quarter wound up pushing its AISC down to $800 per gold ounce. For the year it's forecasting $850 in AISC per ounce, give or take 5%. This would give Goldcorp a very healthy buffer of nearly $400 per gold ounce.

Reasonable production growth is also expected to accompany rising gold prices and low long-term costs. Development rate improvements at Cerro Negro in Argentina, along with the continued ramp-up in production at Eleonore in Quebec, should be the catalyst allowing its gold production to grow by the mid-single digits for the near future. 

Considering that most precious-metal mining companies are valued at roughly 10 times their cash flow per share, and Wall Street is forecasting cash flow per-share growth from $1.50 in 2017 to $2.09 in 2019, Goldcorp appears to be quite cheap at its current per-share price of $13.

American Eagle Outfitters

Finally, I believe investors looking for top stock bargains should take a closer look at mid-cap teen-based retailer American Eagle Outfitters (NYSE:AEO). Shares of American Eagle are down 20% over the trailing year.

What's wrong, you ask? To begin with, weather patterns that have deviated from the norm have left American Eagle's stores filled with the wrong product. This has meant discounting to move unwanted merchandise and lower margins. Secondly, competition from e-commerce giants have been undercutting the prices of mall-based retailers. Remember, physical stores have considerably higher overhead costs than e-tailers. Finally, consumer spending simply hasn't been up to par, leading to American Eagle Outfitters' weaker earnings results.

A teen with a credit card in a retail store.

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However, what investors have to remember is that spending fluctuations are normal within the retail industry, and that American Eagle Outfitters is among the best suited for such fluctuations. The company's management team has a history of moving unwanted merchandise very quickly, such that inventory issues rarely last more than two or three quarters.

American Eagle Outfitters also operates in what I'd describe as the perfect price niche. Competitors such as Aeropostale have struggled with a cheapening of their brand through excessive discounting, while Abercrombie & Fitch has priced a lot of its clientele out of the market. American Eagle occupies a mid-tier niche that allows teens to own brand-name merchandise at a reasonable price without cheapening the brand with excessive discounting.

In addition, the company has wisely been investing in its direct-to-consumer sales, where growth is outpacing its physical stores, while being prudent with capital expenditures. It ended the first quarter with $225 million in cash and no debt whatsoever but is capable of more than $300 million in annual operating cash flow. Expansion is done entirely through the use of operating cash flow.

The result? Buying American Eagle Outfitters' stock right now lands you a top-tier mall-based retailer that's valued at roughly 30% below its average price to cash flow over the past five years and is paying out a market-topping 4.3% dividend yield. Now that's a top stock on sale!

Sean Williams has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.