It was also about parts quality at the time of production.
Omega only used the best, flaw-free parts for chronometers. The company used high magnification with overhead projection to sort parts according to quality. Only the parts that met standards for gearing, functional finish, precision and cosmetic perfection went into a chronometer.
Hoi has shown you the balance poising pocks, which incidentally were placed out of pose to improve the overall accuracy of the watch, but parts 'quality' was also a very big consideration. For example, I have a cal 551 167.005 Pie Pan from 1962 that belonged to my father. It has been regularly serviced since it was purchased. It still maintains accuracy within COSC specs and the only parts that have been replaced are the crystal, case gasket and crown.
Under high magnification, one sees few imperfections in parts of a fully original Constellation, whereas in an unregulated cal 552 one may indeed see some flaws and functional finish imperfections.
That having been said, watches that have not been fastidiuosly serviced and that contain replacement parts have lost some of the special 'chronometer-ness' that was originally present.
Never-the-less, collecting trends dictate that any watch that has 'chronometer' on the dial is probably more collectible than an 'entry-level' caliber that did not receive the full 'treatment' at manufacture.
In the case of Omega, each chronometer was assembled and adjusted and regulated to meet the BO standard of "better than average results" the highest BO commendation. Rolex and other manufactures reserved the "better than" watches for the priciest of the models, whereas Omega would not let a chronometer out of its factory unless it has that appellation. Whether it was stainless or a Grand Luxe, all Omega chronometers were certified at the highest BO level.
The fact that Omega dedicated 25% of its workforce in those days to quality control speaks volumes about the company ethos of providing the best of the best of its output for chronometers. That is the basic reason for the premium we choose to pay for chronometers methinks
Cheers
desmond