Over 50%.*
This includes cables, power conditioning, power supplies, distribution blocks, grounding, etc. They’re all intrinsically linked.** They’re all part of the transmission.
IMHO, it was worth every penny. My very modest system can run with some of the big dogs that I hear at audio shows.
The best part is that I had fun putting it all together. It’s been a fascinating exploration into physics - particle theory and wave theory.
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* This is somewhat skewed since I got some great deals on my primary components.
** Without a transmission, a car won’t function very well. Without a high performance transmission, a Formula One car will not compete very well.