Thing is you have to draw a line in the sand somewhere when it comes to cost, otherwise they just spiral out of control.
I agree with Fred that looking at something like a 150PS TDI GT or R-Line model represents relatively poor value when you add on the costs of the "missing" bits of equipment that the GTD has. I specced one on the configurator a short while ago, and getting a GT DSG to as near the spec of a vanilla GTD as possible, ended up with the GT costing a few hundred pounds more !
On the flip side, if all the extra tech that the performance models have leaves you cold (performance, Xenon's, Climate control, winter pack, 18" alloys etc. etc.), then a standard off the shelf GT or R-Line does end up at quite a but lower price than a GTD. I knwo what I would want and I ordered a GTD (my second).
If you have a budget of say £30k for the new car then a manual or Auto GTD or GTI would be my choice without options (OK maybe metallic paint) with the most expensive of the foursome (the GTI 5 door DSG) coming in at £29,935.00. As I said, it's all about the line in the sand, because if a £30k is your maximum (and that's pushing you), then another £2k for an R (£31,865 for a 3 door manual) to nearly £4k (£33,395) for the 5 door DSG might just be the straw that broke the camels back.
Obviously I'm quoting list prices and I know we would all get discount off these, but I'm pretty sure the price differential between models after discount will still be something similar.