[hylaride]

There is a diminishing return of what percentage you save, sure. But amazon will always be at that edge. They already have amortized the equipment, labour, administration, electricity, storage, cooling, etc.

They also already have support for storage tiering, replication, encryption, ACLs, integration with other services (from web access to sending notifications of storage events to lambda, sqs, etc). Uou get all of this whether you're saving 1 eight bit file or trillions of gigabyte sized ones.

There are reasons why you may need to roll your own storage setup (regulatory, geographic, some other unique reason), but you'll never be more economical than S3, especially if the storage is mostly sitting idle.