's (NASDAQ:AMZN) revenue continues to climb, jumping 22% in the most recent quarter to $12.8 billion. But the company lost money, and the biggest reasons were a 35% rise in fulfillment costs and a 47% jump in technology and content. Both of these costs are due to Amazon's Prime service, and while Prime is fueling growth, it's also killing profits. Long-term, that poses a challenge for investors, who have to begin wondering when Amazon will make a profit.