When that student graduates and joins a Fortune 500 company they are! I've always looked at need-blind scholarships as an investment in a person's future the same way some people invest in stock. They give you money now based on how much of a potential they see for a return on their investment. They give scholarships to try to lure the most successful students to their colleges in order to build a wealthy Alumni association who will keep giving. I know the political science department at my alma mater (the University of Mississippi) recieves a lot of financial support from 2 former governors, the current governor, and both of Mississippi's U.S. Senators, all of whom are alumni. Jim Barksdale (founder of Netscape and another U of Miss. alum) gave the school $5.4 million to build an honors college. I guess to answer your question, undergrads aren't worth that kind of money, but once they graduate a lot of them can be.
Well, these colleges have billions of dollars of endowment. Money isn't really an issue for them. What they're trying to do is get undergraduates with great potential so that they can raise the prestige of the college later on.