I built a server a few years ago in a Fractal Design Node (big square box) which has 4 6TB drives in raid 5 for 18TB of storage and a 6 core AMD cpu. It cost around £1200 and half of that was the hard drives.
It’s been really good, so if you’re looking to build one yourself I’d recommend having a look at the case and the price of drives.
Still weird that they stopped selling them on steam and gog…