Indeed. Prices have been stable more or less for at least two years now. I'm in the same board. Currently I'm using three 4TB HGST drives. (two for data, one for parity) + one 3TB WD drive for data and one 2TB WD drive as a cache drive.

I could just add another 4TB HGST drive, which would undoubtedly be the cheapest solution. It's just that the server is due for a hardware upgrade also since it's using more than 10 year old hardware. Still using an Intel E8400 Duo Core CPU, on a motherboard that was second hand to begin with. I have no idea how long this motherboard still has left, but I already had it happen a few times that the system simply had shut down. No idea why. Could be the PSU also I guess. In any case, I'd like to upgrade it ,and this HPE server look nice. But then I would have too many disks, so I would need to upgrade those as well eg to three 8TB drives. But what then with the old ones?

Aaah, decisions, decisions...