You love buying your shirts when they go on sale. And who can resist a buy-one-get-one-free offer? So when our stocks go on sale, why do we bemoan their low prices?

Smart investors like Warren Buffett or Marty Whitman love it when their stocks are suddenly selling at bargain-basement prices. For them, these companies become no-brainer buys.

The investors in the Motley Fool CAPS community also like a bargain, apparently. Below, you'll find three companies whose shares are selling at least 50% below their 52-week highs, but which still earn high honors from our investor-intelligence database. Consider it a BOGO sale on stocks.

Stock

CAPS Rating
(out of 5)

% Off 12-Month High

AgFeed Industries (Nasdaq: FEED)

*****

60%

Clean Energy Fuels (Nasdaq: CLNE)

****

50%

Momenta Pharmaceuticals (Nasdaq: MNTA)

****

50%

Naturally, we want you to look a bit closer at these stocks before buying. You can get low-priced appliances in the dent-and-ding section of your home-remodeling superstore, but their quality might not be so good. Same thing here: Make sure there's nothing seriously wrong with the company before you plug it into your portfolio.

Take two, they're small
Despite huge pork demand in China, AgFeed Industries was forced to write down a substantial amount of value associated with 31 hog farms it acquired several years ago. The sales increases it saw this past quarter came largely from of the purchase of U.S.-based pork processor M2P2, which it hopes will be the foundation for future growth. Receivables got away from it last year as AgFeed extended generous terms to its customers, and ultimately the company was forced to curtail the practice.

Whether M2P2 will hogtie AgFeed as it runs up against Smithfield Foods and Tyson Foods (NYSE: TSN) remains to be seen, and maybe it's just a stunt to learn Western hog farming practices. But with the company having crafted a plan to spin off its profitable animal nutrition business as a separate publicly traded company, AgFeed's future relies on successful hog production.

CAPS member cnbcgb says the market is pricing all Chinese small cap stocks as if they were the next RINO International, a company that admitted it fudged its numbers and was subsequently delisted. Demographics, however, will support AgFeed's growth.

All Chinese small caps are priced as frauds. I doubt this one is, since it has a respectable U.S. accounting firm, although not a Big 5 firm, and because they have operations in the U.S. Come on Mr. Market. The sale has to end. Bottom line is this is a relevant company for China's consumption needs.

Let us know in the comments section below or on the AgFeed Industries CAPS page whether an investor should get piggish about the stock at its current price.

A reserve player
Some people might assume there will be a technological breakthrough that will sever our dependence on oil to power our cars, but more than likely there will be a gradual transition using technology produced by the likes of Westport Innovations (Nasdaq: WPRT) and Fuel Systems Solutions.

The truck market that Westport is targeting through its Cummins Westport joint venture could be the foundation that gets the national network of refueling stations being built by Clean Energy Fuels rolling forward. A critical mass is developing for alternative fuel vehicles that when broken open ought to sweep Clean Energy higher.

CAPS member nibs61 thinks it's onto something and points to the nat gas specialist's R&D budget as something to look at, but davfoo thinks Clean Energy's got a ways to go yet before it is viable: "I love what this company is trying to do, but profitability is still a little way off. My guess is that this will continue to trend down toward $10 until they start showing profitability."

Wall Street is certainly on board, with all 11 analysts following the alternative energy leader thinking it will beat the market, but you can follow its trials by adding Clean Energy Fuels to the Fool's free portfolio tracker.

On the level
The generic drug business is a cutthroat one. Last year Momenta Pharmaceuticals saw its stock enjoy a brief dalliance at record highs after the FDA approved a generic version of Lovenox, an injectable drug used to prevent and treat blood clots. That was good news for Momenta and its manufacturing partner, Novartis (NYSE: NVS) subsidiary Sandoz. Momenta went on to report better than expected earnings, but news that Teva Pharmaceuticals (Nasdaq: TEVA) would offer a competing generic Lovenox treatment sent Momenta's stock plunging.

Patent infringement lawsuits are a way of life for these companies, and Momenta wasted little time before going after Teva. And little wonder. Aside from the competition, Momenta's generic version of Lovenox allowed it to post annual profits in 2010 for the first time in its history.

Considering the response Teva received from the FDA over its own version, CAPS All-Star TSIF says Momenta will use that to its advantage.

Complete responses, even if minor take time and Momenta may delay [Teva] production further by pursuing patent litigation, (which they are unlikely to win, but could use to delay). Any delay is pure cash to Momenta's balance sheet. In the meantime, Momenta will continue to build out it's generic portolio, most likely with a play back against [Teva] on one of their current drugs, Copaxane for multiple sclerosis. This could be a long term play waiting for one of several possible catalysts, or it could be an exit on another mood swing.

Add Momenta to your watchlist, then head over to the Momenta Pharmaceuticals CAPS page and tell us how big an opportunity this could be.

Have half a mind
Sign up today for the completely free CAPS service, and tell us whether these stocks are twice as good at half the price.

Momenta Pharmaceuticals is a Motley Fool Rule Breakers selection. Novartis is a Motley Fool Global Gains recommendation. The Fool owns shares of Teva Pharmaceutical. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. 

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.