In answer to the original poster's question: yes, reviewers should review mega-dollar cables because it is in their economic interest to do so.
Even if very few of us will ever end up contemplating spending $8,600 on a Kraken power cord, which just received a good review on Dagogo.com, reviews of mega-dollar cables support all cable retailers/manufacturers. The reviews help convince a select few of us to spend absurd amounts of money on cables, e.g. $13K on the top-of-the line High Fidelity Cables power cord, which costs as much as a clean water well in sub-Saharan Africa or one third as much as an in-ground swimming pool. The rest of us see those reviews, dismiss the products as absurdly overpriced, but slowly become conditioned to spend $500, $1,000, or $2,000 on similar cables without compunction, telling ourselves we have found a bargain. Meanwhile, complete strangers to this hobby would tell us to see a psychiatrist.
In any case, those reviews keep this hobby fascinating, providing a window into both behavioral economics and human psychology.