First thing I notice about this graph from Economix: the overwhelming difference between the three bars is the dark blue section representing "parent income and savings." Grants and scholarships, student income and savings, and student borrowing is pretty constant across these income levels. Parental wealth appears to be the salient factor in determining the "typical" amount of money your family spends on college.
Of course, these are aggregate numbers, so it's hard to make general conclusions. If you looked inside the far-right bar, I'm sure you'd find even more reliance on parents' income and less on borrowed or scholarship money at the top few percentiles.