I don’t know if you saw how much WashU has done to make themselves more economically diverse. The percentage of students receiving Pell Grants has increased significantly. Additionally, most top schools are private and cost a lot of money, so it’s not unheard of that most students going there are well off enough to afford it. Either way, WashU definitely deserves it prestige due to their incredible student body, academics, faculty, and the quality of life it provides their students.