I am using a single inexpensive Toshiba Canvio drives at $55 each for a few years now in six different locations/installations. Talk about cheap. The only other part I use consistently are the Rasperry Pi computers with a nice DAC as the receiver plugged into old school amps (tube and early SS). So I am in at around $100-$150 for the harddrive and single pi solution and with the recent pi zero released, my little PC went from $25 TO $5 each putting me closer to $100 for the setup. Nuts.
Here is an example of the pi setup (a bit more elaborate than I use in the power supply - I use a wall wart for a cell phone):
http://parttimeaudiophile.com/2015/05/23/review-raspberry-pi-2-as-music-streamer/
A good primer on networked music:
http://lesbonscomptes.com/pages/homenet-audio.html