a current student here
This is an expensive school, no doubt about it. With tuition clocking in at around 56,000 $/year, it is a substantial investment to go to this school, and both parents and future applicants should be aware of that. That being said, WashU gives close to 50% of its students financial aid, and there are a lot of scholarships that you can apply for along with the general application and it's probably a great idea to do so.
It should also be noted that WashU is one of the best schools in the country, so employers and grad-schools alike know how rigorous the school is, and how much the degree is worth. Research opportunities are easy to come by as are on-campus jobs, so there are a lot of ways to earn money on campus. Overall, WashU is in my opinion worth the investment - but it is an expensive school.