Rolexes are pretty much the pocket currency for the wealthy looking to launder their money around. At one point wealthy chinese business people would book casino trips to Macau, using the what winnings from said casinos so they could to buy up watches and then sell them overseas to get around Beijing’s tight rules about funneling money out of the country.
More reliable than ugly monkey jpegs, much easier to transport than fine art and pricy cars, less likely to get pocketed off than jewelry sitting in luggage at a airport or in a hotel room.