Here is the latest video from Amir on power cords.
This statement is false. Amirm is testing a particular cable- an Audioquest, not all power cords. It would be correct to say 'Here is the latest video from Amir on an Audiquest power cord'.
However, there is a flaw in his testing regime, which is that all power cords obey Ohm's Law; the conditions he set up for testing did not have a great power draw on the cable. As a result, negligible voltage drop across the cord and quite naturally: negligible results.
The benefit of a good power cord IOW has to do with the current drawn through the cord which won't happen with lower powered equipment (for example, an Audio Precision tester).
Power cords that can make a difference don't have to be expensive however! I agree with Amirm that $5,000 should only be spent if it makes you feel better somehow... IMO/IME there's not much use in messing with power cords unless you have equipment that draws enough power to result in a substantial voltage drop across the cord.
I've seen a power cord result in a loss of 40 Watts at full power from one of our amps (the MA-1). That's a pretty measurable result! But the MA-1 draws a bit of power, being a 140 Watt class A triode amplifier.
Put another way, if you want to get the most out of some amplifiers a power cord can really help, and with other amps maybe not at all. The power that the amp draws from the wall plays an enormous role in this which cannot be ignored as we see Amirm doing in this video.