I just emailed a professor I know at SIPA, asking her opinion on SIPA and SAIS vs my less expensive option: GSPP. She said that she "vehemently" objects to the loan burden that Columbia imposes on students, as they'll be paying it off for decades and told me to not think twice about choosing GSPP over SIPA.
It really hurt to give up SIPA and SAIS - they were my top choices since before I even applied to grad school but there is no way I'm risking that much debt when there's a cheaper option (GSPP average debt is 25k, vs 80k at SAIS, and most likely 90k for non-funded SIPA students). I know that many SIPA students get funding their second year but a 20k fellowship barely puts a dent in 140k of debt plus you need to work for that fellowship which means you can't be working/interning off campus to make additional money.
Obviously, you are already competitive since you got into these programs. I agree with GreenDiplomat - if you don't need to go to grad school this year my advice is do everything you can to make your application more competitive and try again next year.