On-demand replication(S3 Batch Replication) cost estimation

Your cost estimation for S3 Batch Replication is generally on the right track, but there are a few points to clarify and consider:

For backup: Your estimation is correct. You've considered the key components: storage costs, S3 Batch charges, PUT requests, and potential inter-region data transfer costs. The specific storage cost will indeed depend on the storage class you choose.

For restoration: You're correct to consider retrieval costs (which vary by storage class) and potential inter-region data transfer costs. However, restoration typically doesn't involve S3 Batch operations unless you're doing a large-scale copy or move operation as part of the restore process.

Additional considerations:

1. GET requests: When restoring data, you'll incur GET request charges for retrieving the objects from the source bucket.
2. PUT requests: If you're copying objects to a new location during restoration, you'll incur PUT request charges in the destination bucket.
3. S3 Replication Time Control: If you use this feature, there's an additional charge of $0.015 per GB transferred.
4. CloudWatch charges: If you enable replication metrics for monitoring, there will be associated CloudWatch costs.

Remember that the exact costs can vary depending on your specific use case, the amount of data, frequency of operations, and the AWS regions involved. It's always a good idea to use the AWS Pricing Calculator for a more precise estimate based on your specific scenario.
Sources
Replicate data from S3 bucket in one AWS account to another in the same region | AWS re:Post
Designing a resilient and cost-effective backup strategy for Amazon S3 | AWS Storage Blog
S3 Replication performance | AWS re:Post