Had mine replaced a while ago.

I don't know the $$ but it isn't just the harness that is the problem (for me anyway), The electrical arcing ate up the metal tabs on the plug socket on the light housing.

Just unplug the harness yourself and take a look at the connections to see what you have to repair/replace.

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2008 535xi:
Sport, Night Vision, NAV, PDC, HUD

Mods
Rear Seat Heat Retrofit, Passport 9500ci, HD Radio Retrofit
Shock Sensor Alarm, Sport Automatic Retrofit , Active Backrest Retrofit, Fire Extinguisher, PROcede with Meth Injection