Like so many of the audio "truths" we throw around, the one that says cables should only cost 10% of your system is overly simplistic, IMO. Yes - when you are buying a new system and you have a limited budget, I totally agree that you should spend 90% on the components. No question. But after you have stuff you really like and want to bring out it’s full potential, I think it’s a good idea to at least try some relatively expensive cables after you have saved up some additional funds. Although I’ve been involved in high-end audio since the Dahlquist/Ampzilla days, I never experimented with more expensive cables until recently and I was very surprised by the amount of improvement that can be gained with better cables. For example, I am currently using a $1500 Purist Neptune IC on a 5K amp/dac combo and I was amazed at the improvement over a very decent Black Cat IC. As I said, if I were building the system from scratch, I would not have done it that way, but I really liked the DAC and amp and was curious to see what a good cable could do. And it did a lot. Just my opinion, but at least it's based on first-hand experience, not something I read.
PS - I just did some quick math and, despite the admittedly expensive IC, I’m only into about 20% of my system for cables. Probably because I don’t have room for heavy power cords. So I don’t feel so bad now. Boy, this stuff adds up fast, don’t it?