For many years, the answer on how much I actually spent on cables was 0.00%, because my amps and sources (apart from the turntable) are from Naim. The cables that came in the box for free were very hard to beat, and so were the ancient Naim speaker cables I got for free when a mate ‘upgraded’’.
In the last decade, I have upgraded a lot and eventually found cables that work better than the originals. However, as others have said “it depends”. Should we allow for how many sources we have, and whether we have separate pre and power and/ or a phono stage?
I’d also say that spending a few hundred on getting a sparks to fit a dedicated electricity supply from meter to hifi had a bigger impact than any power block or conditioner I have heard (some costing over £10k).
Critically, I know that I am a rubbish tester, esp on a quick A versus B test when I know what the new cable costs and how hefty it is. So I get friends (including professional musicians) to help and do actual ‘blind’ listening tests - if a difference can’t be consistently picked in repeated tests without sight of which wires are plugged in, then I am happy to assume that it is in my mind and not my ears. That sort of test has saved me a lot of money, particularly on cables.
Also, ‘different’ is not the same as ‘better’. Many use cable choice (esp speaker cables) like tone controls to get those speakers and that that room just right.
For those who have found a magic cable that makes £1k speakers sound to then like £20k speakers, at least to them, congratulations- I am very pleased for you. Don’t let my (or others) scepticism put you off.