Most of what separates a good garment from an ordinary one is decided before anyone designs it. A fibre is chosen, with a diameter measured in microns and a staple length measured in millimetres. A yarn is spun tight or soft. A cloth is woven at a given weight and finished, or over-finished, to feel expensive in the hand for exactly as long as it takes to get it home. None of this appears on the label, and all of it decides how the thing will look in year three.
The second half is fit, which is not the same as size. A jacket is right when the collar sits on the shirt without a gap, the shoulder ends where yours does and the sleeve shows a centimetre of cuff. Those three points can be bought off a rail or corrected by a tailor for the price of a good dinner, and no amount of money spent on the label will substitute for them.
The third half, if we are allowed one, is arithmetic. A wardrobe is a portfolio: a small number of pieces carrying most of the wearings, a long tail carrying almost none. The desk publishes the cost per wear because it is the only figure that tells you which half of the portfolio you are about to add to.