I reach 25%. Not so much in power but some good money there too. Interconnects and speaker cables. Most Nordost expensive series for a long time now (mostly because I have friends with local dealer and gets back cables almost at the price bought, give the extra money and upgrade). Most of the times, however, I could spot differences only when the gear was of relevant price.
For example when I had upgraded from Red Dawn to SPM reference in a 4k amplifier setup it was difficult to say the differnces. When went to Symphonic Line 20k+ I couldn't believe how obvious the difference was between two cables
I was very impressed these days creating a DIY Neotech balanced cable with Rhodium XLR connectors.