Amazon decided to increase the price of Amazon Prime on Thursday, leading to questions about whether or not the online retailer will lose customers from the margin-increasing move. Judging by how its competition is doing, Amazon might not have much to worry about.

Amazon's subscription service, Amazon Prime, used to cost $79 per year, a prime number, but now the company is throwing away the whole "prime number" scheme and, potentially, a contingent of customers by raising the price $20 to $99 per year. Amazon is giving potential new Prime members seven days to get in on the $79 per year deal (with 30 days of a free Prime trial membership included), but after that, everyone besides students will be paying about $100 per year for Prime.

Backlash to the Increase?

According to a Consumer Intelligence Research Partners (CIRP) poll of Amazon Prime members taken just last month (via CNET), less than half of current Prime members -- which account for about 45 percent of Amazon customers -- said that they would definitely or probably renew their subscriptions at the $99 level. That's down from 94 percent who said they would definitely renew at the $79 price.

The poll also found that if Amazon had increased the Prime membership by $40, which the company was earlier rumored to be considering, as much as 40 percent of Prime members said they would "definitely not review their membership." Of course, that was just a poll, and with the benefits of Prime, customers have to put their money where their mouth is with the new price hike, whenever their subscriptions come up for renewal.

Prime Benefits

Judging by the CIRP poll, and the polling that Amazon probably did internally, a lot of calculation went into the company's price hike, and a lot of calculation needs to go into customers' decisions about whether to drop or keep their memberships as well.

That's because Amazon Prime is much more than a simple customer discount program. In addition to free two-day shipping on nearly anything Amazon ships from its own warehouses, Prime comes with a Netflix-style instant video streaming service with a library of tens of thousands of titles, free digital borrowing of hundreds of thousands of Kindle e-books, and possibly a rumored Spotify-type music service.

Prime Calculations

So with Prime at $100 per year, consider that after about 10 to 15 digital shopping trips, with shipping on many average-sized internet orders often totaling $8 to $10, Prime has still already paid for itself.

The $100 per year is also close to what most Netflix instant subscribers end up paying for their service over the course of a year. The same goes with Spotify or similar music subscription services. And borrowing Kindle e-books saves you around $10 every time you don't purchase one.

The bottom line is that if you're the kind of Prime subscriber that buys a good amount of stuff online and/or takes advantage of the other digital offerings, you'll likely swallow the $20 price increase, especially because over a year that equals less than $2 per month more.

Amazon's Calculations

As Quartz helpfully reminds us, Amazon has been cutting its competition to pieces -- but only through sacrificing its own bottom line.

While Amazon's total revenue has steadily increased quarter-by-quarter, its net income has been unreliable and its profit margins thin. And this is a publicly traded company.

Increasing the price of Prime, if Amazon doesn't lose too many customers, will help boost those margins, now that its competition, like Staples and RadioShack, are actively closing locations and looking for ways to survive, thanks to Amazon and services like Prime.