Unfortunately, the author seems to be doing a bit of hocus-pocus hand-waving to make these "underground" malls seem like some mystical place. If it's too inconvenient for any of you to make it into China, you can always stop by Hong Kong.
In the district of Wan Chai (a fairly touristy area of Hong Kong), there's a fairly well known place known simply as the "Computer Centre". In it, you'll find two floors of a giant warehouse packed floor to ceiling with shops selling everything from a refurbished matte black MacBook from 2006 to an "iPhone 7". I do have to say that the vast majority of the products are legitimate, but there are booths which cater to the less-discerning customers. The great benefit of buying in Hong Kong is that you'll often find products from the mainland side and from the factories in Taiwan.
Sorry if you feel like that, i thought it was pretty straight forward no bullshit article.
You can't really compare these underground markets (That are actually markets, physically under the ground, many of them illegal and only for wholesale buyers) I'm talking about to the shopping malls in Hong Kong which are just flashy shopping malls that anyone can walk in to.
But sure yeah, you can buy things from Hong Kong, its safer, you likely won't get ripped off but at the same time your not going to get rich doing it.
For computer parts, Wanchai computer center is ok, but not the most interesting. I'd give that label to the Golden Computer Center in Sham Shui Po (exit D3 of the MTRC of the same name).
The one in Mong Kok has gone down lately, less shops, more high-end stuff, but there are still some good PC component shops.
Also in HK, you can return something within 7 days if it doesn't work. Beyond that you need to contact the distributor.
These buildings don't have everything though. I'd say that China and Thailand have a lot more to offer in terms of variety.
In Bangkok, the Chinatown area is really interesting. You can buy almost everything if you can find the street or building where a particular item is sold. Last time I was there I stumbled upon a watch market; you could buy them wholesale, by weight (not really, but it almost seemed like it).
In the district of Wan Chai (a fairly touristy area of Hong Kong), there's a fairly well known place known simply as the "Computer Centre". In it, you'll find two floors of a giant warehouse packed floor to ceiling with shops selling everything from a refurbished matte black MacBook from 2006 to an "iPhone 7". I do have to say that the vast majority of the products are legitimate, but there are booths which cater to the less-discerning customers. The great benefit of buying in Hong Kong is that you'll often find products from the mainland side and from the factories in Taiwan.