Do pocket watches exist, how much do they cost and how much do they weigh in D&D in the worlds of classic fantasy such as Faerûn, Dragonlance(Krynn), or Greyhawk? I am interested in the "in-universe" ability to track time up to a minute.
I have found the following comment of Ed Greenwood on sageadvice. According to that, after the Spellplague the use of water-clocks began to spread and large, cumbersome commercial water-clocks costs at least 1000 gp. Ed Greenwood also pointed out that rich merchants, nobles and busy warehousekeepers use pocket watches most often in the Realms; it is customary to wear those watches on a chain around the neck, not on the wrist. I could not find the recommended price and weight for a pocket watch in the official materials.
Editions from 2nd to 5th are of interest. If you manage to find this information, please mention to which edition the material that contains it belongs, if possible. Thanks.
Best Answer
During the 2e era, there was a sourcebook titled Aurora's Whole Realms Catalogue. This is a very interesting accessory as it is essentially an in-world catalog of mostly nonmagical items that could be found in a certain buy-through-mail store in the Forgotten Realms. In that book, we have (pages 43, 99, 147):
In the 5e, the price of an hourglass is 25gp. So perhaps there is some inflation or perhaps some items that require delicate workmanship has increased in price. Taking that into account, and the fact that DaRoni was the Faerun's equivalent of Leonardo da Vinci and was building only as commissioned, and finally the fact that you are aiming much smaller devices, the prices should be above the 1000gp level.
Moreover, it is not likely that the technology level of the Realms is high enough for the construction of non-magical watches. It is likely that they are semi-magical constructs. The church of Gond is very active in coming up with such inventions.