No, I don't think that's the issue. As much as I normally hate on the exorbitant prices people put on the GT4, I genuinely believe that this one is a good price, especially as it's in GT4-only yellow AND the Nismo kit.
A big part of the GT4 attraction is the wheels, and without them it does lose a lot. The rear lights are also a love or hate thing, but if you're wanting a limited edition car you're wanting it to at least look like one externally. Engine/suspension mods you'll probably live with or would do anyway, and to be fair you can get rear lights cheap enough, but the wheels are going to be quite expensive to source. Doesn't help that Cruize wheels are at the lower end of the market too, regardless of how well suited to the car they look.
Get the right wheels and lights on there, and that would sell for over £10K easy. Hell, I'd be tempted at that price!