The cost is determined by the price of your wheat. FREE wheat is VERY cost effective, when I can get it from farming friends or family, but not all free wheat is "good" wheat. You need to know the protein level of the wheat for optimum use. You also don't want to use new-crop wheat for milling. It's best aged for a year or two.
You will also have the expense of a good mill, and I'd suggest a
Nutrimill or a
Wonder Mill. But a good mill will quickly pay for itself if you are going to use freshly-milled flour all the time. A poor-quality mill is not worth anything...and your baking results will show it. I also mill a wide variety of grains/seeds/beans, not just wheat, so that makes a mill even more valuable and versatile. With a Nutrimill you can also mill a fine-grind of cornmeal - a good plus for that particular mill. the Wonder Mill will only mill flour.
With flour milled from pinto beans or black beans, you can make "instant" refried beans in 7 minutes. Milled split pea flour makes into split pea soup in 3 minutes. Mill small white navy beans and add the flour to baked goods to increase the protein
All wheat is not created equally and not all wheat is good for all things, so it's important to understand the different varieties of wheat before buying it. High-protein wheat is best used for bread, low-protein wheat is used for pastry, cakes, quick breads - anywhere you don't want a lot of gluten development. Durum wheat, although high in protein, is best used for pasta and noodles. I keep several varieties of wheat in storage and have wheat priced all the way from free, to the same wheat used for milling King Arthur White Whole Wheat Flour for this region (from a local mill) - which costs $19.99 for 50# (no delivery because I pick it up). I stocked up on several hundred pounds of Wheat Montana Wheat when they carried it at Wal-Mart a couple years ago - $5 for 25-pounds. Prairie Gold wheat from Wheat Montana is probably my favorite. At the time, $5/25-pounds was the most I'd ever paid for wheat. After record high prices, wheat is coming down in price.
White wheat varieties are the best-tasting. Red wheat has that acidic flavor associated with whole wheat that is a turn-off to people unaccustomed to using freshly-milled grain. I use about 85% white wheat.
Whole wheat berries have a lot of uses than just flour. I make my own cracked wheat and bulgar, as well as making wheat flakes, and a fine-grind of wheat to use as farina (Cream of Wheat). Freshly-milled whole wheat flour can be washed with water and the bran and germ extracted leaving only the gluten (the protein portion). The gluten can be used for "fake meat".
So you have to do the wheat math based on the price of your wheat...
-2 cups wheat berries = 3 cups flour
-1 pound wheat berries = 2-1/4 c. wheat berries
-a bushel of wheat weighs approx. 60-pounds and yields 60-pounds of flour (you will get a little more extraction from white wheat than red wheat)
-It takes approximately 3 cups of flour to make a 1.5 pound loaf of bread (which fits in an 8-1/2x4-1/2-inch standard loaf pan).
A favorite whole wheat cookie recipe:
http://www.kswheat.com/recipes.php?id=192
This recipe is so good people don't even realize they are 100% whole wheat.