After about seven out of every 10 stocks added ground yesterday, I opened my evening article with a simple sentence: "It was tough," I said, "to lose money in the stock market today." Nothing could be further from the truth on Thursday, when the Nasdaq Composite posted its most severe losses in more than two years. No, if you owned an advancing stock in today's market you'd probably attract the attention of the SEC as they launched an investigation into how exactly you managed it. Shares of Alexion Pharmaceuticals (NASDAQ:ALXN), Gilead Sciences (NASDAQ:GILD), and Monster Beverage Corporation (NASDAQ:MNST) managed to do nothing but plummet on Thursday, as the sell-off in growth stocks and biotechs intensified. The S&P 500 Index (SNPINDEX:^SPX) lost 39 points, or 2.1%, to end at 1,833.

Alexion Pharmaceuticals took a 7.5% haircut today, the hapless victim of a rapid shift out of biotech stocks. There's good reason that Alexion shares are being singled out by Wall Street: There's a chance its revenues could take a massive hit. The company's main product is Soliris, a product for the treatment of rare genetic blood disorders and diseases.

What's worrisome about Soliris from an investment perspective is its enormous price tag, and the pushback that price tag has been getting from governments both domestically and abroad. The UK's National Institute for Health and Care Excellence refused to recommend Soliris as a cost-effective treatment last month, citing annual costs that can run up to 340,200 pounds per person per year -- or more than $570,000 at today's exchange rate. 

But Alexion shareholders can thank Gilead Sciences for bringing even more heat down on biotechs. Gilead Sciences specifically attracted the scrutiny of Capitol Hill last month, when three U.S. congressmen sent a letter to the company asking it to explain its pricing. While Gilead's Sovaldi, which treats hepatitis C, doesn't approach the cost of Soliris, the $84,000 you'll need to shell out for a 12-week treatment still ain't cheap. With the government taking an active interest in keeping health-care costs as low as possible, Gilead and Alexion are riskier than investors imagined. 

Monster Energy drinks have challenged Red Bull, but is the stock overpriced? Source: Wikimedia Commons

Monster Beverage Corporation also finished as a major laggard, plunging 7% today. While Monster Energy drinks don't exactly qualify as high-cost medical treatments, biotechs weren't the only names taking a beating Thursday. Growth stocks also got hammered, and with Monster shares trading at more than 30 times earnings, it's currently priced fairly optimistically. Considering the fact that sales growth has decelerated from 30% a year in 2011 to just 9% a year in 2013, investors are right to question this Monster valuation.