SUNY is not the choice of "rich" kids, but it's an option that they have in upstate NY. There is Siena, Sage, and RPI. All within a 30 mile radius (or less) and off Route 90.
My entire family is in this area and I know it very well.
I should clarify a step further... It's not really the choice of rich, "academically successful" kids.
Cornell is less than 2 hours from Markoff's home town... It's a much better school and a lot more expensive then SUNY.
The reality is that if we are talking truly upper class kids (which we have pretty much established is not what the perp really was), they can go to school wherever they want (geographically speaking). Location is generally not a serious consideration. Why should it be? They have the means with which to travel.
My guess would be he either didn't have the funds or the grades to get into Cornell and as I said previously, money buys you into better schools.