Id expect that right now demand for Club Sport is high so the dealer doesn't have to work to hard to make a sale. Its not the best month either, the dealers are sitting pretty with lots of new 66 plates waiting to be picked up, their tills will soon be over flowing.
You can pick up a new GTD on a lease for bugger all at the moment which doesnt help the resale values. Ive resided myself to keep mine till next spring at least, its still a great car, still under warranty. Yeah its always nice to have the latest toy but I may go as far as early 2018 before changing, depending how the facelift looks. TBH right now im not dead set on another Golf, Im not even certain ill stay VW.