So basically Rice could triple each school's endowment and still be 4 times bigger than the second largest.

I've never really looked into how endowments are handled. I understand all the restricted/unrestricted stuff, but not the reasoning behind the accumulation of wealth by universities to a level beyond what they would ever conceivably need. Not saying Rice is necessarily there, but I find it hard to believe a school like Harvard actually ever needs to raise another dollar for anything.