The DS212j only costs $200 without the drives. I actually downgraded from a massive fileserver like you seem to be implying, that had 8 750GB hard drives (largest size at the time) in a hardware RAID controller with an i5 CPU, 4GB ECC RAM, etc. because it was way overkill (you don't need much CPU or RAM to run a file server) and used way too much power. The Synology NAS is already low power but it will go into sleep mode when there's no network access, which was important for me. Being able to do RAID-1 was also important. These two features alone would be very hard to implement with something like a Raspberry Pi... I'd love to hear how you could do it all for under $200 (others have already tried). Also, the NAS has busybox already installed so you can SSH in and manually write daemons or whatever, but people already have created Synology packages for most services you can think of so it's very convenient (for me, Crashplan).