I have the misfortune to replace a side mirror with camera on another car. Cost me over US$1000, which included the mirror assembly (a $970 before sales tax mirror with blind spot equipment plus the camera lens pre-installed), plus painting the mirror cap. This is only one single mirror
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Yes, chances are good that you will need a completely different mirror assembly too on the X3. This is not something that you want to do after market, might as well use the money as down payment for a new car.