Benedict Evans has an interesting post on the possible reason for Apple making a gold Watch. A sample:
So (and this is the question that actually matters) why bother? One could argue that it’s a vanity project, or that Apple’s doing this just because it can, or that a few hundred million dollars still matters at Apple (as indeed it does). But I think it’s more interesting to compare it with Apple retail. Despite its prominence, this is only about 10% of Apple’s revenue. It’s much more important as marketing. And it's great marketing.