White flour has a slightly higher protein content (e.g. I bake bread from flour with 13% protein), but the important difference is that it is much cheaper, e.g. at least twice cheaper than whole wheat flour.

The reason for the price difference is unlikely to be due to a more expensive processing technology, but mostly from the economies of large scale processing, because the production of white flour is much greater.

Whole wheat flour has slightly higher amounts of the more valuable nutrients, but due to its high price it is an inefficient way to get those nutrients. A both cheaper and healthier diet can include white bread and larger amounts of other vegetables that are better sources of fiber, vitamins and minerals than whole wheat flour. (E.g. the food that I cook usually includes ingredients like lentils, carrots, parsnips, onions or garlic, broccoli or cauliflower, bell peppers, parsley or dill etc. Spending less on those in order to make more expensive whole wheat bread would provide much less desirable nutrients, so it would be a bad allocation of funds.)

No, it has nothing to do with economies of scale.

Grains contain both starch and oil and when you mill the grains, the oil goes rancid much faster than the starch.

If you remove the oil you have a nutritionally worse product but it lasts longer on the shelves.

That does still sound related to economy of scale. Longer shelf life means you can have a larger inventory.

That highlights the oddity of your calculations. You say that wheat is cheaper, but little about why. If the economies of large scale processing makes more processed wheat cheaper than less processed wheat, then maybe something else would be cheaper if our habits were different. So it's dubious to use the cheapness of white flour to argue that we should eat more white flour products.

"if...were" means nothing today, because woulda, coulda, shoulda. Today white is cheaper, so the calculation stands as it is, and makes for a very interesting argument in today's flood of influencer diets/fads.

It's very unlikely to matter economically for you or me or the op that whiter flour is cheaper. Bringing it up suggests it matters in some other way - like we have an obligation to buy the cheaper option because that has least impact on the environment maybe? But that does not follow at all. I don't think we should award points for originality either.

> White flour has a slightly higher protein content

The bags of 13.5% protein whole wheat flour and 16% (!) protein whole khorasan flour in my pantry are not convinced this is a generally true statement.

Well, see, the problem for me is mostly that white bread is just unhealthy. If I eat white bread, my blood sugar spikes. If I eat while wheat bread, it doesn't. Given the difference in cost does not even appear as a rounding error in my food budget, and that white bread has long-term negative health effects for this diabetic, I'll go with the more nutritious choice over the marginally cheaper one and get almost all my protein from better sources than grain seeds.

Make no mistake: I dream of gorging on delicious chunks of white sourdough bread hot and steaming from the oven. I just have good and indisputable evidence from my test strips that it is not good for me.