In 2009 I bought these two hard drives for $99 each, 1 tb each:
It finally died a few months ago and I was just shopping for a replacement. Seems disks are now about $30 per TB down from $90 per TB 5 years ago, a drop of 66% in 5 years or 10% per year about.
So in 2019, when this drive collection fails, the $99 cost will buy me 25 TB. Which I think will store all the recorded music in history but probably not all my iPhone pictures.
I took a look at the cheapest cloud option, which is MSFT Onedrive for about $0.05 per GB per month. 100GB for $24 per year. $240 for a TB per year.