The secret behind the differing qualities is a secret of Chinese manufacturing that is really simple if you are a company assembling your product in China. The secret is simply that they will build to the quality you wish, that said the higher the quality product, the greater the cost to produce it.
I only learnt this when researching motorcycles and production facilities, was kind of a surprise when that they can tailor production methods that way, same factory producing the same item at two differing levels of quality, kinda of moronic but at end of day its all dollars and sometime no sense
