Dropbox sends data directly to/from Amazon S3 for its storage. Dropbox themselves don't provide any storage. Here is S3's pricing: http://aws.amazon.com/s3/#pr

Dropbox sends data directly to/from Amazon S3 for its storage. Dropbox themselves don't provide any storage. Here is S3's pricing: http://aws.amazon.com/s3/#pricing http://aws.amazon.com/s3/#pricing S3 charges for both storage and data transfer. Their most expensive data storage cost is 0.15USD/GB ie 7.50USD/month for 50GB. The more storage you use, the less per GB it costs, so I'm guessing Dropbox pay a lot less than 0.15USD/GB.