Final answer:
Amazon S3 Glacier Deep Archive is the most cost-effective Amazon S3 storage class for a financial services company to store data for 10 years, due to its design for long-term archiving of infrequently accessed data.
Step-by-step explanation:
For a financial services company that needs to retain data for 10 years to meet compliance norms, and is looking for a storage solution that minimizes cost, Amazon S3 Glacier Deep Archive is the best fit. Amazon S3 Glacier Deep Archive is designed for long-term storage of data that is accessed infrequently and can tolerate retrieval times of several hours. This makes it the most cost-effective option for archiving data that you do not expect to access often but need to retain for regulatory compliance.
Amazon S3 Standard-Infrequent Access and Amazon S3 Intelligent-Tiering are more expensive compared to the deep archive options but offer quicker access to data. Amazon S3 Glacier is also meant for archival storage but has a quicker retrieval time than the Deep Archive, which makes it slightly more expensive. Therefore, based on the need for low-cost storage over a long duration without the need for frequent access, Amazon S3 Glacier Deep Archive would be the recommended storage class for the financial services company looking to store data for 10 years.