Re: Until the price...
"For those of us who still use desktops (or NAS) HDDs are still the best way to go."
If you want to make best use of large HDDs, then you need to front them with SSD caching (read caching and write intent cache) to mitigate the seek penalties.
The size of that cache depends on the kinds of loads you're generating. The way you do it depends on what you have available. I prefer ZFS for large arrays as it's got zero downtime for fsck(*), but you can cache bsd/linux LVM and Windows servers have their own implementations.
"In the enterprise, ideally you want frequently accessed data somewhere quick and infrequently accessed data somewhere cheap and well-protected. The ability to sort data and place it properly keeps the industry going."
In the enterprise old style, that was the case. When you have large scale automatic tiering/caching then this kind of balancing act becomes much easier. That's why ZFS is a godsend when the "infrequently accessed data" suddenly becomes "hot" for whatever reason.
(*) Some of my older installations have 3-400TB of storage onboard. If they decide they need fsck at startup, that makes for a long delay.