Amazon Prime has cost $79 per year since it became available -- a bargain given that it covers both speedy shipping and a whole host of media services. Unfortunately, that low pricing might not last for much longer. During a conference call discussing its fourth quarter earnings, the retailer said that it might raise the yearly price of an Amazon Prime subscription in the US by $20 to $40. It's simply getting too expensive to offer everything at the current rate, Amazon says; shipping costs have gone up, and people are using the media services much more often. There's no guarantee that we'll see a price hike, but it's pretty clear that those future Prime Air delivery drones won't pay for themselves.