Why don't high quality movies make money???

Interesting observation today from a great website -- Box Office Mojo:

"Brokeback Mountain scored eight nominations, more than any other picture. Collectively, though, the Best Picture nominees made up the least popular slate on record, marking the second year in a row that the Academy has not nominated a single movie with a gross over $75 million." (60 million this year!)

Complete List of Nominees & Their Box Office:
http://boxofficemojo.com/oscar/

What does this say about movies and the movie-going audience? The money makers are widely considered poor- or mediocre-quality movies, but the movies with the most nuanced performances and most impressive visual styles don't really make money (of the critically-acclaimed movies that were nominated in the major Oscar categories this year, only Walk the Line crossed the fabled $100 million mark, and just barely). People say this wasn't a good year for movies, but that really means it wasn't a good year for box office (or probably, more specifically, for blockbusters). Why this schism? Why don't people come out for "good" movies? Of course the big money makers like Harry Potter or Batman Begins also cost a lot more to make -- this year's award winners and Oscar nominees almost all had very modest budgets (my point being that these movies have to make more money to be considered successful -- Brokeback Mountain has made about $50 million, but it only cost about $12 million to make).