here are 18 according to TAS...
http://www.avguide.com/article/the-18-greatest-bargains-high-end-audio-tas-197?src=Playback
I would add these:
Bright Star nodes
herbie's Audio Lab tube rings
Canare 4S11 speaker wire
Goertz Micro Pearls ICs.
J River Media Center or even the J River Jukebox. The latter is free!
Various exotic woods as footers available from woodworking cabinet or hobby, shops. cost? Might be free. Results will vary.
DIY HT screen material, < $175 incld. velvet trim tape.
DIY acoustic treatments. Roughly 10% to 25% the price of the standard versions of likewise items..
IEC to NEMA power cable adapters for breaking in power cords, about $5 ea.
STEREOVOX XV2 DIG cable %100 or less in 1M length.