Upgrading wall outlets

Okay, I’ll take the bait.
All major manufactures attempt to hold costs down to be completive. Suggesting additional purchases or modifications suggests more dollars spent for additional equipment can be counter productive to a sale. Some audiophiles always have their expensive gear modified. Why you ask? Because the manufactures attempt to hold the cost down. This is true across the board at all levels.
You are playing devils advocate…we’ve seen this in audio ever since the start up of the internet and on line audio websites.

You mean Caliburn, Boulder, etc, attempt to hold DOWN costs? I don't believe it. Or rather, I believe they attempt to hold their costs down, but not the price tag to he consumer. At a certain level (and maybe at lots of levels -- $2k/meter cables? -- the far and away most obvious selling point is just how damned expensive the product is compared to the alternatives!), higher price tag is what the consumer WANTS, and helps the sale. So the very highest cost/end manufacturers wouldn't, I think, hesitate to supply whatever they felt would induce the illusion of the truly best performance, including supplying dedicated power cords and electrical outlets and hosts of other "tweaks".

Some audiophiles always modify even their expensive gear because they are tweakers and want something unique, plain and simple.

But what, exactly, constitues this "unreliability" of high end audio power supplies that you mention? And how would simlpy changing a household power outlet cause a significant change to the sound (via a change in output to the speakers) from said high end audio equipment?

There is no exact answer but many designs are less than adequate and response drifts both over time and due to sensitivity to operating temperature. These design issues create the mystique of burn in and and keeping equipment always on or warmed up. It is possible to design equipment to minimize these issues but that would mean some folks dismiss the gear as "unresolving".

On the outlet side - the countless number of ground loop issues due to poor design, equipment incompatibility and the wide use of RCA (unbalanced) alone explains why unplugging and plugging something back in will often change the response.

In my philosophy, when equipment performs unreliably you should change it. Whilst others see differences in performance as a sure sign that the gear has resolving power. Sales people will tend to propagate the opposing philosophy to what I hold - naturally, rather than admit that something performs a little inadequately (and perhaps take it back) they suggest instead that the buyer consider to purchase an expensive power cord or upgrade the home wiring because the gear is so resolving it requires it. (In other words, there is nothing wrong with the gear you just bought - look for your problem elsewhere. Rather a convenient an attractive philosophy for a sales person.)

Its not in the interest of amplifier manufacturers to provide high end power cords. Privately, the amplifier designers may not place much sonic value in high end power cords or wall outlets. But sales of expensive amplifiers depend on the audiophile's belief that quality/expense of any component is correlated with beautiful sound.