If you are concerned about the large number of students from wealthy families at WUSTL, it does need to be pointed out that the situation at Bates is not meaningfully any different; it might even be more visible because Bates draws so heavily from the northeast/NYC private/boarding high-wealth corridor.
You could make the same observation about just about all of the most highly regarded private colleges and LACs, and of course there is plenty of wealth at elite publics.