Presently, an 8 TB external hard drive is going for under $200 online. Actually, the price has been going down on this level of storage for some time now and has bounced back up recently, perhaps in anticipation of upcoming holiday sales. Interestingly, overall worldwide sales of hard drives have been falling for the past year. When I refer to "hard drive," I mean mechanical, spinning storage devices or HDD. The alternative is Solid State Device (SSD) or flash drive storage. Quoting from the Statistica Portal article entitled, "Global shipments of hard disk drives (HDD) from 4th quarter 2010 to 3rd quarter 2017 (in millions):"
The main competing technology for secondary storage is flash memory in the form of solid-state drives (SSDs). HDDs are expected to remain the most used secondary storage because of a greater recording capacity, a better price per unit of storage, and a longer product lifetime. The advantages offered by SSDs over HDDs is that they are faster, generally more durable, and consume less power.For example, the new Apple Macintosh Pro model scheduled to ship beginning in December will offer up to 4 TB of internal SSD storage rather than the tradition HDD or hard disk drive storage. The recent advent of 12 TB HDD devices is slowly making some headway. Backblaze.com, a major online backup company oriented towards the online genealogical community, recently released its "Hard Drive Stats for Q3 2017" and indicated that they had introduced both 10 TB and 12 TB hard drives into their data centers.
What does this have to do with the average genealogist? Not much, I am afraid. But it does mean that overall data storage costs will continue to trend down with some fluctuations depending on holiday sales and supplies. What is important to note is that backing up your data is relatively inexpensive and the cost of adequate storage should no longer be a major factor in making sure you have an adequate backup system in place.