At this point, one of the biggest expenditures I have for my homebrew is yeast. It costs me about $6 per Wyeast smack pack, which is what I use for most of my batches. But when I can reuse that yeast, it makes homebrew pretty darn cheap.
For example, a blog post from 3/2 talked about how I wanted to split a batch and propagate two different yeast varieties from this batch.
Looking at the costs of that batch:
10lb Maris Otter malt, at $1.19/lb shipped from 50 pound sack: $11.90
1lb Melanoidin malt, at $1.39/lb from farmhouse: $1.39
5oz Roasted Barley, at $2.20/lb from my LHBS: $0.69
.5oz Challenger hops, at $3.56
/ 4 oz from farmhouse: $0.45
1oz Glacier hops, at $1.65/oz from my LHBS: $1.65
1 pack Wyeast 1728: $6
1 pack Wyeast 2206: $6
I wound up with almost 6 gallons of beer for a total cost of $28.08 - and that could have been $16.08 if I'd been reusing yeast.
But - since I reused this yeast from this batch in two other batches, I can check the costs of one of those batches.
Reusing the lager yeast for an Oktoberfest that I made in April:
8lb Munich malt, at 10.29/10lb at farmhouse: $8.24
2.75lb Pilsner malt, at 1.19/lb from 50 pound sack: 3.28
.5lb Melanoidin malt, at $1.39/lb from farmhouse: $0.70
.12lb Chocolate malt, at $2.20 from the LHBS: $0.27
2oz Mount Hood, at $1.55/oz from the LHBS: $3.10
Reused yeast: free
Total cost for 5 gallons of Oktoberfest: $15.59
Now, granted, there is some fuzzy math here. I'm still out labor costs, water costs, and propane costs.
For the propane, I tend to average around 5 batches for each tank fill, which costs about $15. So, lets tack on $3 a batch there.
The water costs are negligible, but lets pretend it costs $1 for the 10 gallons of water used for mash/sparge, as well as the 10 gallons (approx) that I run through the wort chiller to cool down the wort post-boil.
That's about $4 per batch in propane/water, and since I'm doing this for fun, I'll claim the labor costs are free. Because I can.
So, reusing my yeast on a batch that has $15.59 in ingredient costs, and $4 in water/propane, I still wind up with 5 gallons of beer for under $20. Pretty good stuff. That's $4 a gallon, or approximately $2 a six-pack.
I'll admit there's a bit of bait and switch here. In order to do all of this, I needed the following equipment:
Grain mill for the grain: $100
Drill to run the mill: $40
Airtight container to store the unmilled grain: $25
10 gallon rubbermaid cooler to hold the mash: $50
Propane Burner: $80
15 gallon pot with spout: $100
6.5 gallon glass carboy for fermentation: $30
Fridge for the fermentation chamber: $100
Temperature controller for the fridge: $60
Keg for the homebrew: $25
Fridge for the kegerator: $100
CO2 tank, tower for kegerator: $100
So... yeah. It's easy to see how I'd need to make a LOT of beer to recoup that kind of investment. But not everyone needs a kegerator. Before I bought mine in 2010 I used to just bottle, which required a $15 bottling bucket, some sugar, some used beer bottles I cleaned, and $5 worth of bottle caps. Easy to save several hundred right there.
Also, my initial burner and pot cost a total of $60 on amazon as part of a turkey fryer kit. I ordered a stainless still filter and valve off eBay for under $40, and I used the pot as my mash tun initially. I'd heat the water in the pot, add the grains to the pot, stir, cover, and let sit. Then all I needed was a bucket to drain the wort out of the pot into, to clean the pot, and then boil the wort in the same pot. Granted, that got annoying quick, and the second pot was one of my first investments. I would then just ferment in a closet, without any sort of temperature control. So, my initial investment was a $30 carboy, $2 airlock, $15 bottling bucket, $60 turkey fryer kit, $40 for valve/spout/filter, $20 bottle capper, $5 bottle lids, and the cost of the batch, which I'd let the homebrew store mill for me. So, my first batch was under $200 total, and then each batch after that was only the ingredient costs.
The moral of the story is that once you get past your initial equipment costs, you can make cheap beer that can be better than most beer you buy in the store.
The second moral of the story is that if you're going to seriously get into the hobby, don't skimp on your initial setup. An extra $100 up front would have gotten me a better burner, better pot, and the cooler, all of which make my brew day go a lot smoother. I am able to re-use my initial pot, but I have an old propane burner just gathering dust in my garage.
Hopefully this is helpful if any of you out there are thinking about getting into the hobby.