Yeah, don't fall for that marketing crap. I got one of those peachy letters in the mail a few months ago. I designated WashU on my AMCAS app ($30), and I paid the secondary app. fee ($60?). And guess what: I haven't heard JACK from them since. Maybe I'll get an interview, maybe I won't. Freakin bastards. I think they send all those stupid letters out just to boost the number of applications--a boost that has a twofold benefit:
1) It increases their selectivity ranking, thereby increasing the prestige of the place. I read somewhere that WashU was desperately trying to dethrone Harvard and take the coveted #1 spot on the USNews rankings.
2) It increases their income for each application cycle. Think about it: 5,000 apps, $60 bucks a pop. That translates into a big chunk of change.