I think the key benefit brushed on by this article is the potential 10x improvement in access speeds (which has many applications, beyond reducing your s3 op charges).
> S3 Express One Zone can improve data access speeds by 10x and reduce request costs by 50% compared to S3 Standard and scales to process millions of requests per minute.
> S3 Express One Zone can improve data access speeds by 10x and reduce request costs by 50% compared to S3 Standard and scales to process millions of requests per minute.