Holy crap. In the time it took me to get ready to put 10TB drives into our NAS array, the industry is moving to 18TB.
They will be expensive but geez they even say that 40TB is on the way. They use microwaves to cook up platter and get more density.
For us home users it means buy just the capacity that you need. In an 8 or 12 drive array the smart thing to do is to divide them into two volumes of Raid10. That way you can leapfrog. Don’t use SHR with jumbles of disks. Because rebuilding the array can can unrecoverable but errors.
So for instance, if you have 6TB then you get 12TB total from 4 x 6TB drives. Where two drives mirror each other. Have one spare to slap in. Then the other side uses 10TB drives for a 20TB total.
Then when the 6TB fills up, put them into an archive. And buy say 16TB x 4. That way you are always close to the top of the curve.
Western Digital debuts 18TB and 20TB MAMR disk drives – Blocks and Files
— Read on blocksandfiles.com/2019/09/03/western-digital-18tb-and-20tb-mamr-disk-drives/