Your reporting on income diversity among undergraduates struck home. It's not only money that separates students from different classes. I grew up in a solidly working-class family. Early on in our freshman year, my mother and grandfather decided to visit the campus on Parents' Weekend. I had a one-room double. My family and I thought nothing of having my guests sleep in the room, with my grandfather in my bed and my mother and I sharing a sleeping bag on the floor. It not only saved them the cost of a hotel room but gave us all more time together. My upper-middle-class roommate was horrified, as was our RA.
As a sophomore, a classmate asked me to be her guest at the opera -- until she realized that I had nothing appropriate to wear, at which point she offered to "buy back" my ticket, rather than be seen with someone who was underdressed. A sophomore-year roommate of mine (I later learned) used to show my closet to her preppy friends so that they could laugh at my wardrobe.
I learned a huge amount at Princeton about many things, academic and otherwise, including the differences between the behaviors of working class people and those in the upper middle class.