This is bullshit disguised as economics. It's an MBA's analysis of why they're not allowed in the club, and it's because "it's not cool enough for us."
Costco follows TQM: their business model is integrative and process-based, and takes into account the quality of their product, market, shopper experience, employee experience, and management. This is key. It cannot be ignored or glossed-over or simplified, and any doing so is indicative of an ignorance of the process.
There isn't a lot available about Costco's internal process (that I can find with some cursory googling), but TQM is based on W. Edwards Deming's theories about factory quality, applied in Japan to bring back their entire economy after WWII: https://asq.org/learn-about-quality/total-quality-management... -- I've found this single article which sums up Costco's successful use of it: http://costcoteam3.blogspot.com/2009/06/quality-control.html
From the article:
"The true definition of quality control is the stabilization and maintenance of a process to produce consistent output. The key to Costco's ability to maintain their low prices and quality is because of good wages and benefits." This is an astute recognition of the importance of the workforce in the quality control process. This is, quite simply, the truth.
The blog post also goes into other use of TQM and process control, including statistical analysis of transportation, use of data on a large scale, and using product quality control methods to ensure good final consumer satisfaction. This is all essential to quality, which is essential to their business model.
You can look into details of all aspects of their business, but they will always be secondary to their overarching TQM model—everything is inherited from that. Asking for details about this is like asking what type of screws were used on the Space Shuttle and claiming that's why it actually got to space.
This is not simply a coincidence of market position and product segmentation. It is all a deliberate, controlled process that is repeatable. Most importantly, other businesses can use all of these concepts to also get a repeatable, predictable process-controlled output.
To me, this is not boring or trivial at all. It is paramount to the success of the organization, and an important paradigm shift for all American business. This is something you need to pay attention to. TQM, and more fundamentally Deming are things you should look into and understand, because they are more correct and provable than your standard run-of-the-mill boring old business theory. Even software companies can reap the rewards in process theory and management theory.
The secret of this successful company is actually different, and it's on a high level. You can't just reduce it because you don't like the high level part. Pay attention.