It use to be £15 before the VAT rise.
Its suppose to come standard with the mk6 mind. Dealers try and tell you otherwise.
If this is why your asking tell them the following
"Good Morning,
Thank you for your recent email.
A multi device interface (MDI) is fitted to the new Golf as standard, allowing customers to connect USB players or iPods to the radio. Users can access menus, playlists and track details on both the radio screen and the
multifunction display behind the steering wheel.
The USB connection cable is fitted to the vehicle during production and cannot be exchanged or removed during the process. Volkswagen UK will also be supplying customers with an iPod cable as standard to improve customer satisfaction on delivery.
Cable supply
The iPod cable (part number 000 051 446 C) must be ordered by the Retailer and put in the vehicle before delivery, if your Retailer is unaware of this process please refer them to Volkswagen Desktop Bulletin - 0991-08
I hope this information helps"