I find I can't do that due to bifocals. :I Though it depends on where I'm sitting. I tend to sit around the middle of the theater but I still end up looking out of the wrong part of my glasses sometimes.
The screen's big enough for me to see what's going on anyways. My eyes aren't THAT bad... yet.
There are websites where you can get prescription glasses for far cheaper than $400. Try searching online; unless you want designer frames or have some really incredibly weird prescription that nobody can make, you should be able to get a pair for far less.
Oh sorry, I didn't get that from what you wrote. But I say your vision is important, so get those new glasses and worry about student loans later. I mean, you'll be paying that stuff off until you're 45 anyway.
I wore the same prescription for years and had a similar problem with street signs. Fortunately managed to update my prescription for cheap and can drive safely now. Seriously, though, I could barely read the big E at the top of the test chart.