It depends on what you consider viable, and your level.

As someone in love with fountain pens and ink, I can tell you that there are absolutely wealthy pen turners, private designers, and the same with watches.

highly doubtful if it was your career and you are just starting

probably would make more $ from it if you were a YouTuber or TikTok creator and did "watchmaking" content.

I mean people do make a living doing it, but my understanding is that it requires a lot of hustle—as a hobbyist you can just take your time and meditate and take a million pictures, but if you're trying to make a living you have to focus on volume, volume, volume... So you have to have a system, this one goes in the cleaner and you are immediately disassembling the next, another is in a tray next to the machine that tells you how fast or slow it's ticking... It is maybe less glamorous than it first sounds.