How much is a Cartier watch with serial number 17 050343 worth?

Genuine Cartier watches have a unique serial number. But 17 050343 is a "stock" number put onto multiple fake/replica watches. As such, it is worth whatever someone is prepared to pay to wear an IMITATION Cartier watch. They regularly appear in auction-houses at low prices - I sold one (as a replica) at an auction-house recently for £23.