I got very lucky in that I was offered a generous scholarship to my first-choice school. I realize that this is very rare, but I also worked for several years in low-paying, high-prestige jobs and I think that helped my application (in addition to solid undergrad grades and good statements and rec letters).
If I hadn't gotten a scholarship, I don't know that I would still be attending my first-choice school. It's in an expensive area of the country and you do have to take into consideration the cost of living and the extra debt you might incur in these really expensive cities like DC or New York.
In addition to considering deferring or going to a lower-ranked school that might give you more aid, I think there are two other strategies for advancing your career. One is finding programs that offer evening classes so that you can work during the day to at least cover your living costs and perhaps a portion of your tuition. Some non-profits even offer tuition remission programs and if you get a job at the university you want to attend you can often get nearly all your tuition covered.
The other strategy that people are not discussing here is completely skipping grad school. I know this might be VERY difficult in some career fields such as IR, but there are some high-caliber jobs that can be gotten without a grad degree (some research assistant positions, jobs on capitol hill, some more administrative positions at well-known organizations) that you can potentially parlay into getting a better job down the road or could boost a future grad school application. I know this strategy may not be right for everyone, but I personally feel there is this gospel that grad school is always the right choice for everyone, and I think it's healthy to question that in certain situations. There are people who go far in life without a grad degree. Not saying it's easy, but I respect those people a lot and I don't think they're any less smart than people who get the grad degree. In fact, I've talked to several people who tell me "you don't really learn anything in grad school, it's just about checking a box and/or networking," which is such a discouraging way to look at an education!
The other thing that I would recommend to people who have not already done it is to actually calculate out your cost of living in the future and the impact of a large loan payment on that. Finaid.org has a good calculator that allows you to estimate how much your monthly payment might be upon graduation. If your loan payment is $500, that is an additional $6,000 per year. That may be worth it, but you must remember that the $6,000 is after-tax money, so it's probably more like an additional ~8K that you have to earn each year in order to pay that. I think it might be easier for people that have been in the workforce and have received different level paychecks to understand the impact of different monthly payments on their income.