Its really not that expensive at all, i did a R34 GTR front on my R33 gts-t. The front conversion gaurds and R34 headlights were $2050 to my door brand new. The front bar is about $420 (any gtt or gtr bar will do depending on the bonnet you buy) and i got my hands on a real R34 gtr bonnet for $600.
Except i then had to go an widebody that, thats when it got expensive. But for parts put aside $2000-3000, paint and fit about $800. Not a bad price for something a bit different.
Cheers, Semo
Edit: the lights go on fairly easy by welding on some small brackets, and the bonnet latch can line up if you modify it slightly aswell, no need for bonnet pins. I had some modified R34 hinges put on to hold the bonnet also $70.