Perhaps you can measure things on a scope, but that doesn't mean the difference is perceptible. It's not my money, so I don't really care what audiophiles do with it - but they also seem to expect me to be impressed, which I am not. I politely nod but honestly think they are just burning their money. I can't take someone seriously who thinks that oxygen makes a perceptible difference in audio, and then think nothing of using stranded wire vs. solid. Even with an oscilloscope, the stranded vs. solid will be a much bigger difference than the 97% vs 99.99% copper. And by "much bigger", I mean "still not perceptible".
I know a guy who does installs. He tells many stories, but I like this one: He ran out of super-expensive speaker wire specified by one customer. He temporarily finished the job with landscaping wire, of all things. It was the proper gauge and everything, but cheap stuff that he uses for outdoor installs (which unbelievable people insist on having fancy cable for! Shut those birds up, would you?). He came back later (when the specified wire came in) and told the customer what he needed to do. They guy, completely oblivious to the "problem", was horrified. Just horrified! He had been quite happy with the new system, but now noted that certain things do indeed sound wrong... the brain is an amazing machine.