Have you gotten into any other schools? If so, have you been offered better financial packages? Call them up, and tell them hey, I'm getting xyz $$$ from this school, and I really want to go to your school, but I don't have the financial status to pay for it. Talk to them and see if you can get some more money out of them. I'd imagine your a bright student being that you got into John Hopkins. Get some second opinions on this site first, see what they say, and if they agree with me, then go ahead. I'd imagine your chances greater when your talking in person compared to over a letter.