Thin edge of the wedge effect, I first went for the base model then realised I wanted a bigger SSD, and going to the top model gives you that plus some other stuff for only marginally more than the larger SSD on the base model. At that point, the 460 is only a small amount more, like £90 IIRC, so screw it, the laptop costs like £3k now, might as well.
That's how I went from 450->460 I just wanted a 1TB SSD, and of all the configs that had that, it was such a maginal increased cost to get the faster cpu and gpu I just went for it.