You're comparing a redundant geographically-separated allways-available service with a hard drive that can fail/burn/get stolen.

And if you don't stay with Prime, you just fall back to Amazon Cloud Drive. Their pricing isn't amazing, but not horrible either. $25/year for 50GB.

For comparison, S3 redundant storage is $18/year for 50GB.

https://www.amazon.com/clouddrive/pricing/ref=cd_home_navpri...

http://aws.amazon.com/s3/pricing/