Don't know which country you live in but $160 for a 14 TB HDD is a good price. It's been a while since I lived in North America, but from memory this is a good price for US/Canada.
One general tip for saving space is to get x265/HEVC content, as it tends to be most space efficient on both an absolute and a "quality per GB basis" (some caveats of course, but I digress). That being said you may want to make sure all your clients support x265 (I prefer to simply never have to transcode and have all clients support Xvid/x264/x265 and all major audio formats).