http://sethgodin.typepad.com/seths_blog/2014/03/what-does-its-too-expensive-mean.html Have a read of that and you'll see where I'm coming from.
Gear box is stupid expensive, however that's once every 100k km - hopefully. Plugs are all iridiums (could be platinums now that I think about it), coil packs are about 20% dearer than standard skylines, parts are rarer hence more dorras (window motors, fuel cap release motor, seat motors etc), sway bars are about $350 + shipping from the states because they're difficult to source here, exhausts are more expensive when you include stupid frieght rates. Overall, it all adds up for less performance.