It is similar to one in your photo with three phono connectors and single jack which connects to auxiliary media connector. The cable costs £44.65 inc VAT and like you I could not believe that it would be any different from off the shelf video leads which have exactly the same connections. I tried a number of leads, but none gave me a picture when connected to my iPhone, only one gave a fuzzy picture but no sound. I took a gamble today and bought the Mercedes one which worked straight away with an excellent quality picture and sound - I have just had Avatar playing in wide-screen and feels like surround sound. Under video on COMAND I now get the options of DVD and AUX with settings for Auxiliary connection i.e Colour, Sound, Contrast. wide screen, 16-9 and normal.
I am not sure what is different with the Mercedes lead, but it is the only that works for me, could explain why it is £44.65. By the way I am not sure if it makes any difference, but I do have the latest COMAND software update on my car
I use the Apple composite lead to connect to the iPhone. I am going wire it up so I can connect in the armrest, lot easier then playing around in the glovebox