i've done a rough price up on it, your looking into around 10k for a nice hardcore build.
RB26 head without cams, valves etc = 1-2k
cams and gears = 1k
block prep, port and polish, ecu, tune, pistons, gasket, little tid bits.
the throttle bodies themselves.
its not a cheap build hey, i'd give 10k to get a fully reliable, hardcore high revving motor pushing something chronic like 200rwkw.
bang for buck wise its not worth it, unless you have these parts lying around or are insanely rich.
it will sound madly horny but. that said with the right support gear (diff, lightened flywheel, suspension, etc) it will be a very very very cool sounding, and quick circuit car.