Here is my take:
1 - Go all grain (or as close as possible)
2 - Buy in bulk (especially hops)
3 - Wash your yeast
4 - Brew low gravity ales with low ingredients (i.e. - not IIPA)
There are other various methods, but these will cut down on the bulk of your expenses. I'm a stay at home dad/grad student and my wife is a librarian. We don't have a bunch of extra income, but by doing these things I have cut my costs down to ~$20 a batch, less if there are few ingredients. Most people hit the first three points hard, with neglect of the fourth because they might not want to compromise. BM's Centennial Blonde is a great brew that is fairly cheap to make, I can do it for about $15. Is it my favorite type of brew of all time? Certainly not. I wish I could brew a Imp stout or IPA every time I brew. However, it fulfills my desire to brew more often, tastes great, and most importantly keeps my cost low enough to enjoy my hobby without breaking the bank. Recently, Ive been using the grain bill as a base for some single hop beers, making it even more exciting to see what you come up with in a month or so.
