Earlier quoted context omitted.
I collect watches worth >$100k and I promise you that most collectors in this range are just watch nerds that have more money than they know what to do with. Singapore is a big watch market because it has a very tight knit and wealthy collector community. Margins on most watches in this range are around 10% on the low end. I wouldn't call that razor thin.
What people can actually do is buy a watch then return it in another branch in another country after paying a "restocking" fee.
I say "almost" no dealer because some domestic dealers have a 24-48h return policy but they are pretty strict about these things and care way more about their business than any money laundering attempt. They will be very suspicious of you buying in one country and asking for a return label from another.