xcgirll, that's exactly what helps the most. BU is actually fairly generous, or at least they want to be. They just don't have the money to actually meet the financial needs they calculate of every student they accept/that enrolls. So, instead of randomly determining which students to meet 100% of their need, they offer more to above average students, sort of in lieu of scholarships. (They still have scholarships, but less than most schools I think, and some are designated only for those not eligible for grants)
If your stats are about their average or below, they probably won't give you a ton of grants, even if you need it and get in, unfortunately. Personally, their financial aid was pretty damn good for me, but my SAT/ACT, gpa, etc is a bit above their average. Boston University - Office of Financial Assistance - Applying for Financial Aid
this is a chart, that gives estimates of aid, based on income and SAT and class rank. It's not a definite prediction at all though, and plenty of people have gotten packages that contradict the chart I'm sure.