I think that attitude is one of the problems of American cars. You mustn't make a Chevy as good of quality as a Cadillac. I was very worried that Honda, Toyota and Nissan would follow that model when they brought out the Accura, Lexus and Infiniti. Fortunately they haven't fallen into that trap.
I think that's one reason why American trucks don't seem to have this problem - they don't have quite the stratification of name plates within a company.
Actually, they do. Compare the Cadillac trucks to their Chevy/GM counterparts - or the Lincoln trucks to their Ford counterparts.
The higher scale trucks are screwed together better.