My only guess on this would be to cover the cost of shipping the part from Touratech Germany to Touratech UK.

Have tried to order 4 things from Touratech UK and not one of them was in stock so they all had to be ordered from Germany - Three of the things I ended up cancelling due to TT messing up, the fourth was an order for someone else so that one I waited for.

Unless I have no other choice than to order from TT in the future then I personally wont bother using them again, they just don't really cut it as a quality supplier.