It's been going down a long time. (and I think that XComp ad is from '81) This is what you got in 1956

50 24" platters
$3800 / month lease (you couldn't buy a computer from IBM then )
3.75 megabytes

Click image for larger version.  Name: harddrive2.jpg  Views: 203  Size: 57.3 KB  ID: 43097

https://petapixel.com/2014/10/29/tak...d800-raw-file/

I have our very first Novell file server's HDD sitting on the floor of my office Here's a pic with a much newer (but still quite obsolete!) 500GB 2.5" drive. A Micropolis 1.53 GB drive. We thought that was such a HUGE amount of space at the time. (Our total on-site storage is now on the order of 60 TB ) (I do not remember what we paid for it, but, I expect it was less than $3400, but not by much...

The original photo on my phone would just barely fit on the IBM drive above.

Click image for larger version.  Name: IMG_0420.jpg  Views: 327  Size: 784.4 KB  ID: 43098