Who do I pay for the storage when I use my own S3 bucket?
Short answer: You pay your storage provider directly — Amazon bills S3 under its own pricing, and Storage Studio adds nothing on top. Your Storage Studio licence covers the app. Check the provider's prices for storage, requests and downloads.
You pay your storage provider directly. Bucket storage, FTP and SFTP accounts are your own accounts with your own provider — Amazon bills you for S3 according to its pricing, and Storage Studio doesn't add anything on top.
Storage Studio's licence covers the app itself. Check your provider's current pricing for storage, requests and downloads, since getting data back out can also be charged. Storage Studio's own plans are on the pricing page.