The point of the tweet is slightly different from what you're making though. Your comparison would be valid if the artificial diamonds were somehow cheaper-looking while otherwise performing as good if not better than natural diamonds for use-cases where aesthetics don't matter (drill bit tips, or what have you). But that's not the case, the artificial ones look exactly the same - maybe a jeweller could inspect them and say "ah this one is artificial, I think".
They also mention suffering, which seems kind of hard to measure but I think it's relatively well known that natural diamonds are saddled with a fair bit of baggage in that regard (slave labour, conflict diamonds, things of that nature).
You can't easily map this onto luxury watches, but it'd be like if you could buy a watch that was indisputably a Rolex, was "equal" in aesthetic appeal to its equivalent Rolex while being cheaper and didn't involve whipping the watchmaker who built it or something. And maybe a few watch afficionados with special knowledge of serial numbers could inspect it and go "ah this one was made without whipping the watchmaker"
Thing is, there are inexpensive watches that are well-regarded within the watch community though: https://www.hodinkee.com/articles/a-seventy-five-dollar-watc...
