^Harvard hasn't eliminated loans for all students. In fact, 1/4 of the graduated students last year had loans. Harvard (~$26 B endowment), Yale (~$16 B), and Stanford (~$17 B) all still have loans just like Duke (~$6 B), while Davidson (~$428 million) and Princeton (~$16 B) have eliminated them. I think this is more a difference in philosophy rather than having the financial means to do it. The Stanford financial aid officer explains: "We felt like it was very reasonable to ask students, before we give them thousands of dollars in institutional scholarship funds, to take on a portion of the burden." Duke, similarly, feels that "it is not inappropriate to students to consider helping support their cost of attendance" through loans.
Duke Boosts Financial Aid, But Says Loans Still Have a Role :: WRAL.com
One school you mention, Brown, just became need blind about 3 years ago and still isn't need blind for transfer students. Duke has been need-blind for years, and I'd consider Duke to be way ahead of Brown in regards to fin aid, even if Duke says they will not match offers. Duke's packages are also generally larger than Penn's, as I understand (at least, this information comes from around 3 people I know applied to both and received fin aid packages from both - Duke's was larger. I understand this is a small sample size. And for the only person who asked Penn to match Duke's offer, they didn't, so I guess it depends on the officer/pacakge) While Duke is a step behind the top few players, I'd still say the fin aid program is one of the top ten/fifteen best in the U.S. And while I'd like Duke to eliminate loans such that I don't have to pay them back, I kind of understand why they exist and do think that puts more responsibility on the student, which can be a positive thing if it's not too large of a burden.