Percentage of cable cost

the proportion spent on cable should be related to affect cables have on the sound of your stereo system.

I have never gone by the "percentage" rule with cables. I think that an expensive cable is worth it when it's the cheapest way to improve your system. IMO, a box or speaker upgrade should sonically exceed the sonic contribution of a cable upgrade. But when your system becomes expensive to the point where better cables offer a significant sonic upgrade for much less then a black box upgrade, cables are the way to go. Cables are the icing on the cake, but you need to have the cake first.

I feel cables can make a significant difference, and yes, this has included double blind tests in my system. Current cabling cost varies from 10% - 15%. I do find that used cables hold their value extremely well, so ultimately have spent very little on cables.

I never decided ahead of time I was going to spend "X" percent on cables.. I bought cables I found to be good for my needs. After many years i have added up all my currently used cables, and my current system costs, and gee as if by magic the cost is 10%.

I also like cables which have been around. Like Kimber 8TC, Hero, etc..
Not the flavor of the day raved over today and forgotten tomorrow.