Since I buy in bulk, grow some of my own hops, save yeast by yeast washing, etc, the cost has gone down per batch.
However, saying I homebrew to save money on beer is like saying I'm buying a new car to save gas. Sure, my old 20 mpg car uses more gas, but it'll take a LONG time (maybe not even during the car's lifetime) to say that my new 37 mpg car saves money. The initial cash outlay alone could buy me 8,333 gallons of gas for my old car! But, I want a new car for other reasons.
Same as brewing. My per batch cost is way under $20, but I have a new burner, and all the other gear I've spent money on over the years. Propane costs money each time, even though it's not a big cost. I'm sure I am no where near the break even point, and I still want more gear! I want to get more keggles, and get a brewing sculpture, for example. It'll make my brewdays less labor intensive, but definitely not going to be cheap!