I suspect part of the make up of GTR owners vs Porsche owners is the modifying aspect. Nissans have always been one of the more tunable cars around. And the GTR enjoys the sort of aftermarket support not seen by Porsche owners. Sure there are plenty of parts adn tuners of Porkas, but 15K exhaust systems etc etc normally see most Porsches 95% std. Ditto Ferraris etc.
But buy a Nissan and you can go to work on them as though a blank canvas.
Still, from what I can tell the GTR needs to get back out and get a laptime at the Ring as its slower then the Viper, ZR1, LFA, GT2 etc. Price or not, if you are going to claim its faster then seems thats the yardstick these days