Phong uses a stone tumbler to add wear/patina to his cases. It's a mostly automatic process. His labor involves putting the case into the tumbler barrel along with some type of polishing medium (I would love to know exactly what he is using........so if anyone knows, please let us know) & turning the motor on. Then, he lets the tumbler do its work for several hours to a few days, depending on the amount of 'wear' he wants the case to have. Once the case has the right amount of wear, he takes it out, engraves it (if required, which takes no more than a few minutes) & ships it off.
The cases themselves, as has been discussed many times on rwg before, cost no (or very little) more to make than the average replica case, because that is all they are - replica cases. The quality of the steel is the same, the manufacturing technique is the same, even the lack of QC is the same. The only area where they may differ is in how much effort was spent to match the dimensions of the gen they used as a model. And, considering the amount of variability (lack of dimensional consistency) of all of these premium cases, they are likely made in the same factories along side the average Canal Street replicas.
Frankly, I doubt it costs more than $10 to make any of these cases. Engraving, which just about any jewelry store can do, a few dollars more. Phong, Natalie & others selling these outrageously priced rep cases are simply pocketing huge profits. Now, I will grant that those who operate in the US or EU are entitled to make a bit more profit due to the legal hazards involved in their business. But selling rep cases & dials for more than $300 is really outrageous. But, as they say, value is what a buyer is willing to pay &, when it comes to watches, especially vintage Rolex watches, neurotic WIS types (like me) are not always playing with a full deck.