Customers will be able to tag ECR resources and attribute costs based off of tags.
Terraform support for this: terraform-providers/terraform-provider-aws#6923
Terraform support will be released as a part of AWS provider version 1.53.0, later this week: https://github.com/terraform-providers/terraform-provider-aws/issues/6896
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https://aws.amazon.com/about-aws/whats-new/2018/12/amazon-ecr-now-allows-repository-tagging/