I chatted briefly with the author of this piece, who said that apparently the only people making money on these watches are online "marketing gurus" who will teach you how to get rich selling free watches.
It's absolutely true. I sell screen printed t-shirts that I design and print myself, as a hobby, and as such I spend some time trying to improve my sales. The facebook group I'm part of is lousy with people trying to sell these same cheap watches, jewelry, etc., complaining that they can get lots of traffic via Instagram but no sales. I would wager 50% of them at least will never make a single sale. The rest might make a few sales but never come close to a positive ROI.