Why high-end cable manufacturers don't post measurements?

Transparent is the worst offender. Their cables have "Networks" that are enclosures somewhere in the middle of the cables. What's in there? They ain't talking. I owned a cheaper model and the network was made of plastic. The cables were balanced so there were 2. So I broke it, but I got it open. There were shunt filters which consisted of a cheap Radio Shack capacitors in series with an equal quality resistor going from the mains into the ground lead. So in theory they could have "shunted" some HF noise, but these were $350 20 years ago. Their top of the line speaker cables, The MM Opus, has a network the size of a football and it's made of a sealed composite. Only 40 large. 40 big ones for a cables they won't even explain how it works.

Coz it is mostly snake oil. 

Mr. glupson

Dayan was a big art (archaeology) thief. Mayby, the bigger in Israel ever.

Well, cables recommended did have a larger than common cross section.
Yes, it is a bit tricky to connect such a cable to the Amp and Speakers binding posts. But it is solvable. There are plenty of ways, most involve a short tail, of a less thick cable (like # 8 awg).
The difficulty should not be an obstacle in your way to get better sound.
Really better.
The #14 or #12 awg cables (most of them in the speakers cable market), are convenient to work with, but they do not do the job and do not sound good.