Two questions to make you mad.

Was the difference worth the cost for you?  Only you can answer that question.  Same for every other individual that is inclined to be frugal or go big $ with their system.  Broad generalized statements that cables make a huge difference or can't possibly make a difference are worthless.

Similarly, extrapolating and extending must include all the variables involved when comparing which AC cable is used in audio versus another application.  No doubt Audio Precision power supply, filtering, grounding, shielding, components, construction, etc. are designed to handle the good, bad, and ugly AC power.  All Audio components are not necessarily designed to the same standards.  Different AC cables may, emphasize may, make a difference in the audio realm.  

Refer to the work of Galen Gaeris to learn the science involved in cable design.  Reviewers and other opinions based only on R, L, and C only scratch the surface.  Everyone does not need a cable designed by Galen Gaeris.  Neither is it correct to say there is no difference in cable performance.

Try different cables, or not.  Just don't claim what worked, or not, for you can be universally applied to every other situation.  Same for reviews or measurements - no universal truth to be found there. 

@texbychoice Thanks for the thoughtful post and the reference. To your question I bought a Boulder Preamp and that made a huge difference, and I just added 2x power filters (old Firman AC conditioners) for my Subs that are always noisy, I've been fighting with them for 4 years I love their sound and I really should know how to get rid of the hum but I have had only bits of luck here and there. Moving speakers around made a huge difference lately but honestly I don't think any of my cables really have made much difference I haven't spent a lot on cables probably just under 10k $, probably a much lower % of my system price than most here. But I do have about 18 of my speakers that are powered (the future), those speakers are  super precise and have the best imaging I've ever heard (Genelec "The Ones"). Good cables are important but AC doesn't work on the audio side of quality equipment it's all run on the DC side so as you said the transformation to DC is the important part.

@donavabdear Glad you found items that made a difference. Our Audio Hobby can be a never ending journey of different equipment and tweaks.  If we could all start with stable and clean AC that would be a great start to eliminate one variable. Stand alone filters, conditioners, and regenerators all can give you good AC. AC cables, not necessarily expensive, made of quality materials and construction are important to minimize  pollution of a clean AC source. 

Start with clean AC and convert to stable DC in each component.  However, audio remains a variable frequency and amplitude signal to process keeping unwanted noise at bay.  Our home environments typically include cell phones, computers, smart TVs, Wi Fi, Bluetooth, and various convenience electronics that all contribute to EMI/RFI pollution.  All that electronic noise can still cause problems with our audio equipment.      

A Power Regenerator eliminated my system sounding different morning, afternoon, or evening.  Prior to that several other "tweaks" made differences that were both audible and measurable. Each change was based on improving the quality of items like wire, capacitors, resistors, connectors, etc. Cost does not have to get out of control. Made my own quality shielded interconnect cables. Properly grounded everything, avoiding ground loops.

AC cables are a work in progress. Ditched the cheap manufacturer supplied cables and made one of my own and tried a couple reasonably priced "audiophile" cables.  For my system different AC cables made much less difference that the Power Regenerator. 

Everything matters, to a varying degree, due to many factors unique to each of our systems and environment.

Best of Luck.