i admittedly do not know a lot about MPH/MD programs, but aren't they normally 5 years? in that case, then, being able to complete the program in 4 years would save you an entire year of tuition, no?? i know that Tufts has an exorbitantly high tuition, but does shaving off a year's tuition compare to what the other schools you're applying to will ask for over the fifth ("extra") year?
the other consideration is your time....will having one year taken off of your education justify paying more for the other years? there are a lot of people who would yes and a lot who would say no, but that's your decision and definitely something worth considering.
lastly, how many MD/MPH programs are there out there and how strong is tufts'? it might be worth it just to apply and worry about money if it comes down to it...as in, what if it's the only place you got into....would you ultimately go when you consider money/time/location/program strength? as one of my friends pointed out to me, once you get in somewhere (if it's the only place you get in), you will have a hard time denying an acceptance and reapplying to a school you'd rather be at, so take that into consideration when deciding if you should apply or not.
if i'm completely mistaken, sorry!! hopefully, though, this will help!