My experience too, in general WK (!)... but with one
major exception.
Against my better judgement, a mate at Superfi persuaded me to buy 4 speaker 'jumper' cables a few years ago. I said
'only if I can return them for a refund if I hear no significant improvement'. Remarkably this was agreed, and I handed over c. £75 for these 4" bits of wire (the Boss thought I was bonkers until I explained the 'deal'). Back home, a few hours later, jumpers fitted... and all thoughts of snake oil had totally evaporated. Not just for me, but for the Queen of Sceptics, too! The difference was astonishing and I reluctantly decided that they had to stay.
I suppose it's possible that spending daft money on speaker cable improvements might have a similar dramatic result, but I've never been flush enough to risk it (there IS a limit to my occasional rash spending on hi-fi)!! ATM I'm still perfectly happy with my (relatively) cheap Van Damme blue speaker cable