I think the big thing to remember with GTRs is that actual general running costs are not that much more. I just found that if anything did go wrong or any modifications cost ALOT more as GTRs are that much harder to work on, labour costs go through the roof compared with GTSTs or more of your own time is spent doing these things.
Three little examples I had with my GTR:-
1) blew a turbo exhaust gasket. Removing those turbos cost alot of time just to replace the cheap gaskets, may aswell replace turbs or at least change the dump pipes while going to all that effort. . . . . .
2) Air leak developed on the rear throttle body, again massive labour time to remove the plenum just to replace some cheap gaskets. . . . . .
3) Modified the sump with the TRUST sump extension and baffles to help avoid those nasty oil surge stories we here about when enjoying the GTR at the track, engine out job. . . . . mega hours. . . . .
Whereas on my GTST had a cracked exhaust manifold and some broke studs, a few hours job done. . . .
The sump on the GTST had a nasty dent, again, sump replacement, a few hours and its done. . . .
That for me is the difference between the costs of owning the 2. And for me, since I like doing the track days often the GTR became a little too much in the running and maintenance costs so hence to return to the GTST.