It is the data centers. I was given an opportunity to invest in one recently, and the pitch deck estimated the storage requirements and costs. They made it a point to say "estimated" because costs are rising rapidly. This data center planned for an initial purchase of 1.8 MILLION drives, (YES, MILLION!) a mix of SSD and HDD. As it turns out, that crazy number appears to be just barely above the average for these centers, some centers are larger, some much larger. One of the major variables in the deck was the unknown annual increases in replacement drive costs.
Edited to add that CHIPS were also a MAJOR cost, and again, they plan for significant increases in the future.
Given that, it should be no wonder as to why storage costs are increasing. After I heard the "pitch" I went directly to my K account and ordered a 120TB Terra!
Jim