How do I know if seller is selling genuine cables?

Only buy from persons with many killer feedback then pray.

"So I guess the answer is to buy from a reputable seller w the understanding that you have the right to return if the manufacturer says they are not genuine."

Wouldn't the obvious sub par sound tell you it's a fake?

Given how system=dependent cables, i am not sure that how they sound is a reliable indicator, unless you had another known genuine reference. YMMV.

A fake does not mean that it will sound bad. The two do not go hand in hand. Think about it!

Fake boobs look great and many times perform better than the originals, and they cost more! ;~)

I've purchased cables here(verified authentic via serial number/dealer contact), without issue. Lately; I've been purchasing everything through The Cable Company(http://thecableco.com/), enjoying their, 'Frequent Flyer' discount and removing all risk.