Agree. The new wide event pipeline should fully utilize cheaper storage options-object storage like S3. Includes both cold and hot data and maintains performance.
deleting data early after moving it to cold storage, has additional costs.
sc1 HDD-based volumes are cheaper than S3, while st1-based volumes are only 2x more expensive than S3 ( https://aws.amazon.com/ebs/pricing/ ). So there is little economical sense in using S3 over HDD-based persistent volumes.