> it's hard to fathom that a private school is providing adequate value for the cost difference.

Agreed. I'd rather my kids attend the best in-state public university, assuming they can get in, rather than pay significantly more for them to attend a private university. A private university that offers significant merit scholarship would be fine, but I'd look at what is required to keep those scholarships.

I have young kids, and I expect college costs may change a lot over the next 15+ years. I'm hoping public universities will do more to control costs and limit tuition increases, or more states may roll out Bright Futures style programs that cover some or all of the cost of tuition at public universities. I'm therefore going to hold off on sinking a ton of money into 529s until my kids are older and I know more about what their college costs might be.