The first thing a genuinely good tailor does is talk you out of something. Not out of the commission — out of the particular idea you walked in holding. A shirt that costs a week's rent is only worth making if the collar sits correctly on your neck, and most collars, on most people, do not.
Hong Kong has no shortage of shirtmakers, and the range in quality is wider than the range in price. The ones worth returning to are rarely the ones with the most impressive shopfront. They are the ones who ask questions before they reach for a tape measure.
The collar is the whole shirt
Almost everything a shirt does well or badly is decided at the neck. A collar that stands away from the throat looks slack no matter how well the body fits. A collar that presses too tightly will never be comfortable, and no amount of fabric quality rescues it.
What a good maker checks is unglamorous: how the collar band sits against the neck when you turn your head, whether the points stay put under a jacket, whether the interlining is soft enough to move. In a humid city the interlining matters more than usual, because a stiff one will wilt into a rag by early afternoon.
Shoulders cannot be altered, everything else can
This is the single most useful thing to know before commissioning anything. Shoulder width is a function of the pattern, not the fitting. If the shoulders are wrong, the garment is wrong, and no amount of taking in the waist will fix it.
Everything below the shoulder is negotiable. Waist, sleeve length, body taper, hem — all of it can be adjusted in a second fitting. Which means the thing to be fussy about during the first measurement is not the silhouette you have in mind, but the shoulder line you actually have.
The tailor who agrees with everything you say is selling you a shirt. The one who pushes back is making you one.
What is worth paying for
Not the fabric, usually. Within reason, a well-cut shirt in ordinary cotton will look better than a badly-cut one in something expensive, because the fit is what the eye reads from across a room.
What is worth paying for is the pattern — the thing that determines whether the shirt was drafted for a body like yours or for a hypothetical average. It is invisible, it is slow, and it is the entire difference between a shirt that looks intentional and one that looks borrowed.
After that, the honest answer is that most of the premium goes into details only the wearer will ever notice. Which is not nothing. A shirt you can forget about all day is a specific kind of luxury, and it is the one that actually gets worn.
The best tailors in the city are not cheap, and they are not fast. What they offer is not really a garment. It is a set of measurements that will still be correct in five years, and the quiet confidence of knowing that nothing on you is fighting anything else.