Amazon just hiked the cost of Prime membership by 16% to $139 for millions of its existing customers. The new charges start Friday.

• Existing Amazon Prime customers will begin to see a new higher price as their memberships renew.
• The monthly rate is now $14.99, up from $12.99, and the annual cost is $139, up from $119.

The price increases for Prime that Amazon announced back in early February are finally arriving for current members.

Starting Friday, existing Prime customers will see a new price hit their bank statements when their monthly or annual plans renew for another term.

The new monthly rate is up $2 to $14.99, while the annual rate is up $20 to $139, an increase of more than 16%. New customers have been presented with these higher prices since February 18.

When it launched Prime in 2005, Amazon charged $79 per year and has since raised its price twice: an increase to $99 in 2014, and $119 in 2018.

More recently, Amazon has come under scrutiny for its sign-up process for Prime, which some customers have said led them to feel manipulated into signing up, according to internal company documents obtained by Insider's Eugene Kim.

"Unintentional sign-ups erode customer trust," one of the documents said. "Either way improvements in clarity during sign-up are needed," another document said.

An Amazon spokesperson said the signup and cancellation process are "simple and transparent."

Prime has more than 200 million members as of last year, making it one of the most popular subscription programs in the world.

In addition to free shipping, Prime members can access Amazon's streaming services for video, music, and gaming, as well as member-only deals and discounts at Whole Foods, which is owned by Amazon.

The average Amazon customer uses the service a lot, with the typical customer making 74 delivery orders per year with just one or two items per transaction, according to the shopping analytics firm Numerator.