SAS storage is cheaper and better than SATA
SATA and SAS have got cheaper, and SSD is slowly getting cheaper. For storage, I use https://www.hostxnow.com/backup-hosting - not the most competitive pricing around for most people, but it supports everything like SFTP/SSH/Rsync which a lot of the other big brands don't support. The backup storage plans at HostXNow are hosted on SAS drives which is much faster than SATA. SSD is too expensive to be used for storage servers at the moment.