Well, in Xanathar's Guide to Everything there's the Orb of Time. It's a common magic item that, using an action, can show you whether it's morning, afternoon, evening or nighttime; it basically works like a pocket watch. Common magic items are around 100gp. That points toward the most basic version of a pocket watch being around that price.
Those 1000gp are for a water clock, which is a huge bulky thing that barely fits into a room; it's more like a tower clock. It's very expensive because you need a huge amount of material.
It depends, though, in which century your adventure takes place. Lantan reaproached in the late 15th century, so a pocket watch shouldn't be a huge hassle in that time period.
With that considered, a pocket watch is often a fashion item (somewhat). It could cost from 100gp to way over 5000gp (IRL there's a difference between Casio and Rolex as well, so there's no reason why it should be different in any D&D world).
Any experienced craftsperson should be able to build one if it's invented yet in your setting... or maybe a player character IS the inventor of those devices... I mean, why not? Artificers are a thing in Faerun, so there should be at least the possibility for your players to obtain such a thing early on without letting them decide whether they want cool magic items OR a lower fashion item like a pocket watch.
IMO 1000g is a bit much for a basic item. Compare that to other items that have a mechanical use and ask yourself whether you want your players to decide whether they want to flavor up their character OR being mechanically useful. I mean, why not both? Because most of your players will always prefer mechanical use over flavor... flavor isn't worth anything if you die the next day. I'd go with the lowest price you find for fashion/flavor items and give them to your players for the most basic version of said items.
As a DM (for over 20 years) I always went with "Whatever suits the character concept!"... and it always paid out to not be a jerk about it. It suits the fun of the game. So if a player wants to play a former merchant that once had a big business running but is now a rogue... I really don't see any reason, why said character shouldn't start with a pocket watch "for free" at character creation.
Disclaimer: I don't want to impose anyone my style of play! I just made the experience that's mostly often a good thing to give your players the most puzzle pieces you can offer to flesh out their characters early on.