Purely for entertainment value in work we had a look at some interconnects.
we used a R&S ESU26 26GHz EMI reciever and a R&S SMC100B signal generator.
EMC32 cable loss calibration routine. we also used a VNA on the cables.
I cant remember the exact results, but the expensive cables we tested were no better than the cheap ones, infact at high frequency they were worse.
The best bandwidth cable was my home made interconnect using some rosenberger silver cored double screened extra low loss RF cable, where the loss was neglible up to 1GHz where there wers some anomalies due to RCA connector mismatch. The cable would be good up to 20GHz
The second best was a twisted pair made of AC power cord.
even the cheap argos lead was only -1db at 500MHz
None had any measureable insertion loss at any frequency that you would hear. infact the lowest capacitance and resistance was the twisted pair.
we tested 9kHz to 6GHz
I wont be spending my hard earned on posh cable!