Much of the ES stuff is exactly the same as the "mass market crap". Looking through Sony's service manuals many ES and non-ES products even share the same service manuals.
I noted that you did say "Much of the ES stuff ..." and thus left room for possible exceptions, one of which I will describe:
About a year ago I bought a Sony 222ES CDP of 1987 vintage. At home I took the hood off and found a neat layout, an anti-resonant ceramic transport chassis, Duorex and Muse caps, a 2-2.5 mm thick steel bottom plate, a Bando transformer, an OFC detachable mains cord and plastic injection mouldings exhibiting engineering forethought towards rigidity. There was something glued to the hood; it's some kind of resonance deadening material.
Soon thereafter I compared the Sony's sound with three other CD players I have here: a NAD 502 and a Marantz CD-6000OSE. These are what I call 'mass market' units with some 'integrity'. Then there was my Kenwood DP-990SG — definitely not mass-market and seriously crammed full of discrete electronics and a metal die-cast transport. So the Sony was flanked on one side by an upscale, vintage CDP on one side, and two representatives of a more developed technology on the other. Well, I was impressed to the extent that I promptly adopted the Sony into the family line-up.
As a comparably vintage player, it is a bit late in the day to worry about the Sony's bang-for- the-buck factor. But let us review some differences among its contemporary stable mates:
The differences between the 222ES and 777ES model are very considerable — no doubt there. But the ES concept at the lower end may have been to take a more bread and butter design and throw better build quality and superior parts into it. Thus the 222ES and the 333ES are a foreshadowing of a richer taste — not exactly high end, but a distance away from the mass-market drones that were out there at the time. Once you get into the 555ES you are into die cast transport parts and an upscale PSU. Then there is the 777ES — nice machine, and if I ever find one (or a Sansui 717) at a good price on one of my trolls I will fish it out.
Shortly after I bought this unit, I went to the local Sony Corp. offices and servicing depot here in Sendai where I had some work done before. They were very good to me and provided some photocopy pages from the CDP-222ES service manual. I can report that the manual is distinctly model specific. (BTW transport spares are still available.)
Although I am instructed and cautioned by your posting, at the same time I am a bit concerned that your statement might be misunderstood by some readers. Sony does seem to get a bad rap from audiophiles. And these days, as good, affordable audio seems to be threatened by a number of factors that we can't get into here, I think that even late-in-the-day congrats are in order for decent products which show some integrity – even for an industrial giant like Sony. And, even if it is only to encourage the board of directors in the future.
My current collection consists of 12 different manufacturing names from Japan, Europe and America. Among my Sony units, there is a 333ES cassette deck which rivals my Nakamichi 480 for sound, and in terms of utility thrashes it. The TC-D5 portable recorder enjoyed a production period closing on 25 years, and it remains an impressive, never-to-be-repeated engineering and production achievement to this day.
From what I have seen on the reseller's shelves here, the older Sony 'ES' products were built to a price reflecting various grades. They seem to have competed very well with comparable offerings of the day from industry rivals, and at least in one case inspired an industrial and marketing competition that produced some brilliant examples of very affordable audio technology which remain collectibles nearly 20 years later. I could start naming, pointing and comparing and you may or may not be impressed. Let's just say that while I am enjoying my ES CDP, I'll also be looking out for what you say.