You
do need a quality cable for USB, because even though it's a straight data pipe that will not - cannot - alter sound, USB is not a protocol that guarantees delivery. It's like UDP versus TCP: you get one chance to transmit the data; if it gets scrambled, tough luck. So a flaky cable is bad news.
The good news is that a high-quality cable costs considerably less than $3500, about $3490 less.
So much misinformation exists on the web, wrapped in jargon and delivered by people who obviously know more about it than you do. Serious-sounding articles that explain how you can lose fidelity by
copying an audio file from one disk to another, or that USB
makes audio sound bad. Or how about "
a $100 Apogee cable will make as much difference as a $3000 D-A converter"? It's no wonder so many folks are routinely duped into believing technically unsupportable myths - after all, it
must be true if you've read it on the internet.
The really bizarre phenomenon is expectation bias, which really
can make the $3500 USB cable sound better! Or a $2000 power cord, or
magic rocks or green magic markers. If you spend any time on Gearslutz it will become obvious that gullibility runs rampant (actual example: "I have listened to many many things that null and are much different sonically...tests can be deceiving").
And don't think you're too smart to be fooled by expectation bias. None of us are.