I only do feed in the 'bag cycle', scratch grains are estimated but pretty accurate.I like what @aart says about bag cycle. Start a new bag of food, save receipt or write down the price, start a tally of how many eggs you get until the bag is gone, then you can get a basic calculation of how much you are spending on a dozen eggs. You can even add a new bag of oyster grit and/or bedding at the same time if that's something you purchase. Depending how much food your flock goes through a week this method may or may not take you some time. For me a 50lb bag lasts about a month, which would give me a more accurate calculation than a week because it would factor in the girl occasionally not laying.
The other things don't fit the bag cycle(way longer cycles here) and so are calculated annually instead. The longer you keep records the more accurate your analysis will be.
If one is doing this to figure how much one should charge when selling eggs, don't.
Start your egg prices as high as you can for your area,
easier to reduce price later if necessary,
than increase it because you're losing money.