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With the S&P 500 in negative territory since the start of the year, several high quality stocks have found their way into the discount bin and can now be purchased at bargain prices. With that in mind, we asked our team of Motley Fool contributors to share stock ideas that are currently trading at attractive prices that they believe will make excellent long-term investments. 

Dan Caplinger: It's rare that the most valuable company in the stock market is also a bargain, but that's the case with tech giant Apple (AAPL 0.02%) right now. The stock currently trades at just 13 times earnings, and a nearly 2% dividend yield adds some valuable income to what has been an impressive run of long-term share-price appreciation in recent years.

The concerns about Apple center on its relative lack of innovative new products, with the company simply coming out with new iterations of core franchises like its iPhone series. Yet Apple has worked hard to demonstrate the value of its ecosystem, and that encourages those who already have Apple products to upgrade regularly. More importantly, at current prices, Apple doesn't absolutely have to keep growing at the pace it has in the past. If it can merely sustain its current earnings levels, it can justify its current valuation without much difficulty.

In essence, Apple gives you a solid company with the added bonus of potential massive future growth if it can come up with another innovative product at some point in the years to come. That kind of opportunity doesn't come around often for a blue-chip stock, and Apple's combination of stability and potential rewards make it a good bargain for investors to look at more closely.

Alex Dumortier: I know many readers will think I've lost my mind for mentioning troubled automaker Volkswagen AG (VWAGY 0.85%) as a "best bargain." Bear with me.

Sure, there's a reason Volkswagen is cheap: a huge emissions cheating scandal that has global scope and is unprecedented in the company's history. No question about it, the scandal that has engulfed the company has impaired the value of its equity. But does the share price decline fairly reflect that impairment, or does it overstate it? There are good reasons to believe it's the latter.

Here's one example of how this may have occurred.

The fundamental question that current or potential Volkswagen shareholders must grapple with is estimating the total cost to the company of the scandal, including (but not limited to) fines, legal settlements, and the indirect cost of lost sales.

One of the most prominent costs is the fine Volkswagen will incur from the Environmental Protection Agency (EPA), the government agency that first accused the company of violating emissions standards.

It's now common knowledge that the maximum fine Volkswagen can receive is $18 billion, which represents $37,500 for each of the 482,000 Volkswagen cars in the U.S. on which the cheating software was installed.

In this case, the conventional wisdom is wrong. The $18 billion figure, which has been widely circulated, is incorrect and significantly overstates the potential fine.

One diligent analyst, Max Warburton of Sanford A. Bernstein, dug into the EPA regulations and found that the maximum fine for a 140hp vehicle is $21,775; furthermore, the fine is degressive beyond the first 10 vehicles: for the 100,001st car, it's just 3.2% of the fine on the first car. Mr. Warburton estimates that the EPA fine is capped at $7.4 billion. The difference between $18 billion and $7.4 billion is equal to 19.63 euros per Volkswagen share -- nearly a fifth of the shares' closing price on Oct. 8.

Some shrewd observers believe Volkswagen is undervalued. New York University valuation maven Aswath Damodaran values them at nearly 139 euros under what he calls a "likely scenario". The Financial Times' flagship daily opinion column, Lex, puts the value at 130 euros. The shares closed at 103.50 euros on Oct. 8.

Volkswagen looks like a bargain due to an overreaction to the emissions cheating scandal; however, investors are warned that this is a speculative situation in which a permanent loss of capital is certainly possible. 

Brian Feroldi: Forgive me if I sound like a broken record, but the market valuation around Gilead Sciences (GILD -0.21%) continues to simply astound me despite the fact that the company continues to put up impressive numbers and raise guidance, so I still think it's a top place to put new money right now.

Gilead currently holds dominant positions in two diseases, Hepatitis C and HIV, which produce gobs of revenue and profits for the company. The company has also built a huge pipeline of potential compounds that are currently being tested in 36 different clinical trails, with many of them in late stages. While some of these compounds are designed to sustain Gilead's leadership position, others are designed to enter new markets. In fact, the company is currently working on cures for Hepatitis B and AIDS, and given the company's track record I certainly wouldn't bet against it succeeding. 

Currently the market appears to be worried that competition from the likes of AbbVie's Viekira Pak will make the profits from Hepatitis C treatments Sovaldi and Harvoni disappear, but I think those fears are simply overblown as Gilead's Hepatitis C profits have continued to grow since Viekira was launched. The fact that a certain political candidate has turned prescription drug prices into political theatre recently certainly hasn't helped the share price either.

But when I step back I see a company that is growing fast, gushing cash, buying back its own stock, and paying a small dividend, all while trading for under 9 times 2016 earnings estimates, and I tend to get excited. That's simply a combination that I find too hard to pass up, which is why Gilead is my favorite idea for new money today. 

Selena Maranjian: There's a lot to like about Amgen (AMGN -0.71%) these days, such as net profit margins topping 25%. That's right -- for every dollar the company takes in from sales, it keeps more than $0.25. It's also a cash-generating machine, with annual free cash flow topping $8 billion. That gives the company a lot of flexibility to take advantage of opportunities. 

Still, the most important features for investors to assess in biotech companies are approved treatments and ones in the pipeline. Amgen recently won approval for its LDL-lowering cholesterol medication Repatha, and that's a big deal, as more than 70 million Americans have high LDL levels. The drug does have competition, and its price tag of about $14,000 annually may be challenged, with high-priced drugs garnering more media attention. It has plenty of other drugs on the market, though, with sales in the first half of this year of about $2.5 billion for Enbrel, $2.3 billion for Neulasta, and about $1 billion each for EPOGEN and Aranesp -- among a handful of other growing performers. Amgen is also developing biosimilars, for which it sees potential annual revenue of more than $3 billion. 

In its last quarter, Amgen topped analyst expectations for revenue and earnings-per-share growth, posting, respectively, a 4% and 8% bump over year-ago-levels. Even better, management upped its projections. Last year the company announced plans to file for the approval of, or to present late-stage data for, 10 therapies between 2014 and 2016. Meanwhile, with a forward-looking P/E ratio near 13, well below its five-year average P/E of almost 16, Amgen's stock is appealingly priced. The stock also sports a dividend yield recently topping 2%, which has more than doubled over the past three years. 

Sean Williams: It's far from the fastest growing stock in the world, but when it comes to bargains for both value and income investors, I have a hard time finding a more attractive stock than automaker Ford (F -0.81%)

The easiest reason to like Ford is that it's doing a great job of listening to its customers and giving them what they want. We're seeing more technological luxuries in the cabins of its vehicles, and best of all it's not causing the price of its midrange cars to shoot into the stratosphere. We're also seeing a discernible push toward its EcoBoost engines, which provide better fuel efficiency without sacrificing power when needed. And, of course, Ford knows how to hit a variety of price points to appeal to as large a population as possible. 

Ford also has the most loyal customer base around, at least according to IHS Automotive which looked at 16.5 million new-vehicle registrations and discovered that Ford owners were the most likely to stay within the brand. Comparatively, rival General Motors is clawing back from more than 30 million recalled vehicles in 2014, and overseas rival Volkswagen dropped a bombshell last month that it's essentially been lying about the emissions rating of its diesel engine vehicles. While no saint, Ford is looking like a trustworthy name in the automotive sector.

Lastly, think about the global opportunity waiting in the wings for Ford. It's eventually pushing for 10% of China's rapidly growing auto market, while also making inroads in India and other emerging markets. Ford's global opportunity is far from saturated. 

Thus, with Ford capable of $2 in EPS by as soon as 2017 (current stock price is around $14), trading at a PEG ratio of just 0.4, and yielding in excess of 4%, I'm ready to suggest it's one of the market's best bargains.