Inc. (AMZN) reported its fourth-quarter results on Thursday, blowing past Wall Street estimates for earnings per share by $0.28. Sales during the holiday season were 15 percent higher, and sales for the year were up 20 percent.

Amazon reported earnings of $0.45 per share, while analysts polled by Thomson Reuters had expected earnings of $0.17, sending the retailer’s stock soaring more than 7 percent in after-hours trading. Revenue for the quarter came in $340 million lower than expected, at $29.33 billion.

Earnings per share fell more than 8 percent from the same period a year earlier, largely due to increasing operating expenses for the retailer, which rose more than 14.6 percent, to $28.7 billion. Expenses were driven largely by a 29 percent increase in "technology and content" costs for the retailer. CEO Jeff Bezos said the company had invested $1.3 billion in Amazon’s streaming video service, which competes with Netflix but is offered for free to Prime subscribers.

Amazon’s sales were up 20 percent for the year over 2013. The company also announced that its Amazon Web Services cloud business was growing, with 90 percent more customers in 2014.

Earnings trounced estimates thanks, in part, to a rise in the cost of the retailer’s premium membership program, Amazon Prime. Despite the higher price, Amazon said the number of Prime customers rose 50 percent in the U.S. and 53 percent worldwide.

"When we raised the price of Prime membership last year, we were confident that customers would continue to find it the best bargain in the history of shopping. The data is in and customers agree," Bezos said in a statement.

Amazon’s operating income was up 15 percent to $591 million, and it projected first-quarter sales between $20.90 billion and $22.90 billion. The surprise comes after two consecutive earnings misses for the online retail giant.