Calculating cost by amortizing your equipment is pretty easy, but very unnecessary for a hobby. For a hobby, I wouldn't worry about equipment cost, just ingredients.
For brewing management, figure how long to ferment, bottle condition, and then consume. Time it when your last 6 pack is about to be consumed, your bottle conditioning batch is done.
Not at the brewery, but at home on my homebrew system, I have one fermentor and keg my beer (bottling sucks, IMO). I keep a hefeweizen, dunkelweizen, and weizenbock on tap at my house all the time. The hefeweizen and dunkelweizen get drank the most and the weizenbock less as it's not session strength. It's about 3-4 weeks to drink one 5 gallon keg of the hefeweizen or dunkelweizen and it ferments for 10 days then is chilled and carbonated over a week in the cellering room. Usually in a week or two after that it gets brought up to my home office to serve.
Just time it out. For me I figure 3 weeks from fermentor to serving. I have a 10 gallon system at home so one brew is two months worth of beer. When I change out the keg for a fresh one, I brew that style of beer next. I have three kegs for each style so I can be serving off one keg and have two kegs in the cellar ready to go when that one is empty.