Amazon.com reported a 77% slump in quarterly income and forecast a potential operating loss in the current quarter, as the company invests heavily in video content and in fast-growing economies such as India.

The company’s shares, already up nearly 41% this year, were down 3% at $1,014.75 in after-hours trading.

The world’s largest online retailer forecast an operating income of $300 million to a loss of $400 million for the current quarter. Analysts had expected operating income in the third quarter of $931 million, according to FactSet StreetAccount.

The news appeared to be an old refrain on Wall Street: While Amazon consistently posts blockbuster sales growth, its profit has often not kept pace due to thin retail margins and high investment to expand the company’s already vast reach in the U.S. economy.

From its origins as an online bookseller, Amazon has jumped into areas that historically had barriers to e-commerce, from apparel to appliances. The specter of Amazon’s…