I also think besides emissions some customers, maybe more than we think buy these cars for looks and social status. A pure performance version will turn away many customers for being too loud, uncomfortable or too raw. Another considerent is that for a 100k there is always a much more performance oriented beast available and they do not want to undercut it with the lower models. I remember in the 80s when a lot of muscle cars were more affordable, as well as a lot of mid price range japanese sports cars, nowadays not so many. Maybe it is just my impression i did not actually compare how many models and what prices they had.