Which Amazon S3 storage class is the MOST cost-effective for long-term storage?

Amazon S3 Glacier Deep Archive is the lowest-cost storage class in the cloud. It is designed for long-term data archiving that is rarely accessed. It offers a retrieval time of 12 hours and a durability of 99.999999999% (11 9’s). It is ideal for data that must be retained for 7 years or longer to meet regulatory compliance requirements.