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.