The real world is much sloppier than any book will ever tell you.
> is about the development cost vs maintenance cost
Absolutely true.
> how the latter beats the former
If you're believing that equivocally ((I don't think you personally are btw) then I don't think you're reading the advice the book is giving you correctly.
A shitty technical solution that gets to market quicker often (not always) can make the company more money in the long run. There is no "one right answer" here, it's all about judgement. 100+ tech DD's and counting...I've seen the whole spectrum. I've seen a $40M revenue (38% EBITDA) tech company built using a FileMaker-like tech stack (all WYSIWYG). And yes, I'm serious.
Code that doesn't do the job is worthless, no matter how testable and well-designed it is.
Of course you can debate whether this is a management (scheduling, resource, PM) problem or a developer (competence, architecture, tool choice) problem - most likely some of both.
But whoever is responsible, it's still a non-solution.
Not everything needs 90% test coverage and more comments than code to be good. And not everything with 90% test coverage and more comments than code is any good at all.
BUT - when someone else new comes along to look at it, the 90% code coverage, and comments helps them immensely - they can get up to speed to fix whatever bug has appeared a lot quicker.