The price of £300 a wheel is very conservative if the price of Glendales on the Mk6 is anything to go by. The German deals on e-bay at around c£2000 are considerably cheaper than buying from your local VW dealer.
Astronomical mark-up given the price that the manufacturers sell to VW, the cost to VW will be less than £100/wheel according to a friend selling OEM to VW in Germany. To give you an idea, A 14" alloy rim for a Polo some years ago was less than £15 !!