I think the key point in Rich's post was (bolded):
However, I have been tipped off by DC editorial sources that the numbers that DC Comics received were a lot lower than expected. A lot lower. Less than you might expect for a new Superman title relaunching the character with A-List talent and spinning out of Action Comics #1001 and DC Nation #0 and more like – well, a newly launching Brian Bendis title at Marvel, without the tiered variants.
Basically saying "it's selling what you would expect a 2017/18 Bendis comic to sell", whereas DC may have been expecting more like 2007/08 Bendis when they greased his palm...
There's no way DC were expecting MoS #1 to track sub-100k.
For one thing, despite your last sentence, it's the rare exception that sales actually grow - both Superman & Action are likely to be
de facto capped at the orders MoS gets.
For a second, they're not shoving out "BENDIS IS COMING!" ads for literally months on end just to see a
launch lower than the *normal* sales of
Batman - MoS #1 has to be one of DC's biggest issues of the year (not AC #1000 big, but still Event Big, comparing to the likes of Doomsday Clock & Metal) to justify the level of promotion they're giving it, when allowing that it will basically be downhill from there.
And third, both Superman & Action are dropping to monthly as part of the relaunch (not to mention the cancellations of Super-Sons, Supergirl and New Super-Man), and I doubt Bendis is on a lower writing page rate than Tomasi/Gleason or Jurgens. It's too crude to say it needs to sell twice as much per issue to justify it, but it certainly needs to be
waaaay ahead of where the prior runs were to stand still from a profit standpoint, and they were both in the 40-50k band. A
settled level 60-70k is unlikely to be enough, never mind a
launch.