WD now offers their NAS (wifi) drive in 6T capacity for $349.00. I have a 4T and it is full of TV programs so I guess I will have to get another or move up to the 6T.
It is cheaper to get a cheap raid box and stuff a couple 4T drives in it than it is to get the 8T drive.
Big drives require big backup drives, I have a Drobo 5N with 5, 4T drives in it, one failed last week and it took about a week to repair itself, now have to replace the bad drive.
My first hard drive was a 5 meg that I bought used for $400.00, bear in mind that a 400 k floppy was about $400.00 at the time. My first 1 gig drive I paid about $750.00 as I recall, now a Terabyte drive is 1000 times more capacity and can be had for less than $60.00.