You're leaving out things like ops & security staffing, etc. not to mention the physical hardware other than disks: you need servers, cabinets of disks, etc. all of which need to be purchased, monitored and replaced just like everything else.
An SSD might use less power but you need more of them and the rest of the storage server won't change at all.
Finally, I'd love a citation for any compression + dedupe savings at the level you're seeing for large heterogeneous deployments, not to mention reliable performance at their scale.
Do they specify the VMs tested? AWS has a lot of different versions of things in play and most of the people I know fall into two camps: fairly generic VMs running compute jobs, which probably would compress well, and VMs running huge databases / image farms / etc. which do not. By VM count I'm sure the former dominate but by total storage consumption I think the latter wins – I would, of course, love to see if anyone has hard data.
AWS doesn't have that many OS versions.
Besides I'd expect huge datasets go either to S3 or to ephemeral storage like Cassandra clusters etc.
EBS isn't the best place for it. Your mileage may vary etc.
An SSD might use less power but you need more of them and the rest of the storage server won't change at all.
Finally, I'd love a citation for any compression + dedupe savings at the level you're seeing for large heterogeneous deployments, not to mention reliable performance at their scale.