....I think you must have missed out some words because I can't make sense of your sentence.
So, casting aside that most buyers make comparisons between cars within the constrains of their cost budgets, which car would you compare with the Mk6 GTI? And which would you compare with the RS? (only taking into account cars which are currently available to buy).
Segmentation m'man, segmentation. Marketing stuff. GTI faces off against the ST, the natural competitor for the RS would be the VXR Nurburgring edition, Sport Megane hatch renaultsport sport cup sport, and GTI Rwhatever/Scirocco Rwhatever, and mebbe the S3.
It's why people will suffer a diesel Golf and not pay a few pennies more for a GTI; and why people will pay for a Cayman as opposed to a Boxster.
Hence, the BMW X6 - no one asked, no one wanted, but if you build it they will come.