I am sorry but I dont know what you mean. I beleive the steering wheel is an option from the factory and was fitted when i got the car. This does operate the stereo not sure about MMI but I would think it works with a RNS factory unit.
I dont know about cost as i never bought it or selling it.
I've seen you retrofits and I love it,great job
is that steeringwheel functions compatible with MMI system and how much ?