VCGirl, it's NOT going to be ANYTHING even close to $800K.
And keep in mind, you do make a little bit of scratch during residency, which you can (and will) be using to start paying down the loans. No, it won't be funtastic, but you won't actually owe very much more than any regular US citizen would anyway.
The slight difference in interest rate isn't enough to justify putting off med school for several more years, since each year you put off is basically coming off the tail end of your salary as a doctor.
Basically, if you planned on retiring at 65, you'll be losing a few of the LAST years of your salary as a full-time doctor, because you'll have less total years as a doctor. So unless the difference in interest exceeds how much you expect to make in the last few years working fulltime (I word it this way because a lot of doctors keep working part time but are really semi retired at the very end of their careers, but going to med school later wouldn't trim those years, it'd trim the full time years down assuming you decide to retire or semi-retire at the same age).
Trust me, there's no way the 2% or so difference in interest is ever going to justify the salary loss. Then again you do make a decent amount in your current job unlike most of us, so maybe the math actually makes sense for you, particularly if you want to go into a low paying specialty or something. But if you think you'll be in a fairly high paying specialty it'd make zero sense to delay this.
Anyways I have NO idea where you're getting this 800K thing from. And even though it is going to be insanely expensive anyways (although again, not nearly 800K) it's not that much cheaper for anybody else, so the only thing you should be considering is the difference. And that difference will not be a lot.
The only thing that it'll really end up doing is making you pay off the loans more quickly, whereas someone else might put their salary towards investments and hold their loans longer hoping that their investments will grow more quickly than their interest does.
And keep in mind that many (most?) residency programs provide housing along with the salary (or at least subsidized housing), so even though you'll be making a mere $50K and paying a ton of loans, you can get by on somewhat less money because of the nonexistant or low housing costs.
Just a random example:
http://www.twhresidency.org/public/index.cfm?WebPageID=21&CategoryID=6&TheMenuItem=6
It's a family medicine residency so maybe they're sweetening the deal more than usual, since this one happens to include even DSL and phone service in your salary package lol.
So other than the cost of food and transportation you'll basically be able to put the entirety of the rest of your salary towards your loans.
Of course there's a whole issue of taxes too, but your student loan interest might also be tax deductible, so I'm not really sure how it would work out in the end. But more or less I think I could scrape by on $10K a year post tax in food and transportation costs (lol, come to think of it I scrape by that on that now more or less), leaving anywhere from $20K to $35K in post-tax money to pay down the loans (again, this seems to depend a lot on how the tax deductions work, I have no idea).
Regardless, I would go if I got in this year instead of worrying about deferrals, so long as you can find a US co-signer anyway.