Sorry to nitpick, but the GTR's VR38DETT, whilst an amalgam of various Nissan bits, is an all new engine - requiring its own production and assembly lines.
The AWD system in the R35 is vastly removed from any other AWD system on the market - let alone that of the R34 and previous. With the R35, the gearbox is on the rear axle and it does not have the rear axle steering of the R34. The GTR is as much of an "all new" car as the LFA is. A key difference is in the use of lightweight, exotic materials which are far more prevalent in the LFA than in the GTR.
To get any V8 engine over 4 litres to rev to 9000 rpm - you need very special engineering and an exhaustive R&D program.
Take nothing away from Nissan though, how they managed to price the GTR (in the US especially) is something of a miracle for me considering that there was no significant carry-over tech from the R34.
The VR38DETT isn't as "Brand New" as you think it is. I'll try to find the article where it talked about it but that engine is basically using some internals that Nissan used for their racing program. Thus, the engine is VERY compact even though it's a 3.8 Liter V6 compared to their VQ series 3.7 liter engine; hell, it's even in the name VRH was the racing engine and this begins with VR. So while the VR series of engine is brand new to Nissan, it's not as Brand new when you take a look at Toyota's new V10. That engine has been built from the ground up, which they surely got help from their Formula 1 program and nothing even close to it existed before.
As for the GT-R lacking HICAS (4WS for the rest of you), yes that is due to the new layout of the drive-train, etc. And while the layout is different, the ATESSA-ETS system isn't a Brand new system. It's an improved version specifically engineered for the GT-R due to the layout.
The GT-R is all new, but when compared to the LF-A on part-per-part basis, it's not as new. Once again that is due to the fact that Nissan has a lot of stuff on the GT-R that they "made brand new" from their original pieces, while Toyota has nothing to go on besides their JGTC experience (using old school Supra) and their F1 program.
You are right about the use of "exotic materials" on the LF-A. LF-A is more than half using CF and uses of other exotic materials such as Titanium valves, etc., which points even more in the direction of their Formula 1 program.
As for GT-R's price. It has a lot to do with them spreading the cost of R&D over the years to develop the car and using tech (but expanding on it) than building from scratch. Also, they could've used more CF etc, but that would put the car over the price limit that Nissan Exec's have set for the car.