I am also struggling with this conundrum, but I gotta side with this response from a different forum....
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If someone is selling a product with faulty/inadequate power cables, I'm pretty sure there would be recalls and/or lawsuits.
Rather than a safety concern the scam artist's sales pitch says things along the lines of "The inadequately thick (meaning gauge) cord they gave you for free is choking your amp from receiving the full current in needs to provide you with the punch and dynamics your amp is actually capable of". See their story is the necessary cable is "Just too darn expensive for them to give you and still sell the unit at a competitive price." What they count on is that the typical consumer has no idea that thick power cords are actually a relatively trivial expense to the maker. All they see is that Monstrous Hype AC cables are expensive so that's their frame of reference.
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To the general audience now.
The notion an amplifier maker has the wherewithal to design a competent amplifier but either due to incompetence or malfeasance only supplies an inadequately thick (gauge) AC power cord to provide maximal performance with it (considering how incredibly affordable they are when bought in bulk), is laughable.
The aftermarket AC power cord industry is predominantly a scam. Sure if you lose the original cord, need a longer one (which if significant may require a bump up in gauge), or think the appearance matters because you've been told you should, fine. But the sound does not change.
THE LAST LINE SAYS IT ALL!