CEO Mark Zuckerberg of Facebook. (Photo: AP)

Shorting stocks requires nerves of steel, but when it pays, it pays big. Most investors and advisors had no interest in “shorting a cultural phenomenon” when Facebook debuted its IPO, and the idea of a bear bet against the social media giant seemed insane on its surface.

But after a 45% drop in the time since, certain European investors that bought structured products benefiting from the stock’s decline have generated returns of more than 500%, according to Bloomberg.

The news service notes that a put warrant, a security for speculating on the future direction of a company’s share price, which predicted Facebook would be at $22 by March, cost 6 euro cents ($0.07) to buy in the week after Facebook went public with an initial price of $38. Today, with Facebook trading at $21.87 at 09:50 a.m. in New York, the warrant is worth 36 euro cents, according to data compiled by Bloomberg.

Facebook, which raised $16 billion in the biggest technology IPO of all time, hasn’t closed above its IPO price since its first trading day and has fallen 21% since reporting earnings on July 26 that showed slowing revenue growth and narrower profit margins.

“If you bought the $22 put when Facebook was trading at $38, then you will have earned a lot of money,” Heiko Geiger, head of public distribution for Germany and Austria at Vontobel Holding in Frankfurt, which issued the $22 warrant, told Bloomberg.

 “Unless you intend to speculate on prices falling further, it would be good advice to cash in now,” Geiger added.

Facebook’s first earnings as a public company, reported on July 26, showed second-quarter revenue growth of 32%, the slowest pace on record. Operating margin, excluding certain costs, was 43% in the second quarter, a decline from 53% a year earlier, amid a fourfold surge in sales and marketing expenses.