biochimia

The parameter store was not available at the time Strongbox was designed and developed. The Strongbox project page has a nice matrix comparing how Strongbox stacks up against Parameter Store.

In terms of not using credentials directly, relying on AWS KMS for encryption keys, and the use of IAM policies to control access to secrets, Strongbox and AWS Parameter Store share a similar design.

The charges are for the AWS services that Strongbox uses to implement its functionality. That's $1 per KMS key, which can be used to manage multiple secrets, plus the cost of the storage backend. In the most common setup, DynamoDB tables are being used for this.