Watches are the commodity of choice for corruption in some circles. I know people in jewelry and a significant portion of their transactions are watches to Chinese businessmen, formerly through Hong Kong, now through Singapore. They're high value items with razor thin margins.
Most of the time you can wear a watch through customs and move $250K without anyone blinking an eyelid. If it has a box and papers you mail those ahead of you. (Don't have them in your luggage)
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.