Amazon is about to raise the price of its Prime membership service for the first time ever in the US, bringing the cost up to $99 per year, $20 above where its been for nearly a decade. The price change goes into effect on April 17th, and those signing up or renewing their service before then will still be able to pay the original, less-expensive price. While Primes offerings arent changing alongside the price increase, Amazon is citing Primes increasingly substantial offerings as reason for the jump. It notes that there are now more items eligible for free shipping under Prime and points to Amazon Instant Video, access to which is now included in all Prime subscriptions.