In the case of Rolex, billions of dollars. It's one of the most recognized names in the world and by far the most widely recognized name for a watch, and is the reason why so many non-watch folk flock to its banner.
Of course, since Rolex case backs are designed to be opened and closed with a special wrench that not all watchmakers had, a lot of case backs got ruined and ended up being replaced with ones having different reference numbers.
A true Rolex would only have an aegler 15 jewel movement signed on the bridge or ratchet wheel post 1915. Other brands under W&D were sold at lowers costs compared to the rolex brand and would never feature a subpar 7 jewel movement. If its not signed rolex then its not a rolex. Even Rolex-Marconi signed movement is NOT a rolex.
Uh-oh, a web search of just "M832118" gets several results on it being a serial number that appeared repeatedly on counterfeits. I'd like to see higher resolution photos of the movement to help identify it. It appears to me to be a Swiss ETA 2836-2 movement, like roughbarked said, rather than a Rolex movement.
With four or five large, well-equipped buildings in Switzerland, Rolex is well positioned be vertically integrated and manufacture all their own parts. A possible explanation of why viral videos exist that claim important and/or luxury goods are actually made in China is presented by "The China Show" channel: (Warning - video has foul language.)
For example, in the tritium period of early 60's to about late 90's, Rolex had used atleast 5 different variations of tritium dial markings.