[thaumasiotes]

Comparing tuition at Cabrillo College (community college for Santa Cruz, CA) and SJSU (California State University in San Jose), it looks like a "normal" course costs $574 at the bottom-tier 4-year university vs $230 at the community college. If you take 2 or fewer classes in a semester at SJSU (as a full-time student, you're supposed to take 5), tuition falls nearly in half to $333 per class.

$6000 tuition per year is high enough to be prohibitive for some people. But those people are the focus of intensive recruitment and financial aid efforts by universities all up and down the hierarchy of status. That isn't the first place I'd look if I were seeking to answer "why aren't more poor people going to college?"