If you want the ultimate GT-R, what about just bringing in a standard car and taking to it with a spanner and strip the interior yourself. I am sure that will save more than 60kg in itself.
Then with the money saved (or from the bits that you have sold on eBay to some chav that thinks the seats will look great in his Micra), buy the useful parts from Nismo.
I have to agree with the sentiments that this is just a ploy to make Nissan some money. Why don't they just bite the bullet and say... "We messed up the pricing, we're putting the standard car up a couple of grand, but hey.... its still a bargain".
It's all about the twisties....