How do the economics pan out? Do you pay more for gluten at higher purity than the ~10% you get when you buy it in sacks of flour?

The retail case is interesting, although maybe not indicative of wholesale

I suppose this is a function of whether gluten is a usable by-product of making low-protein cake flour. In that case i would expect industrial bread to simply add by-product gluten to cheaper flour. But that might obviate the search for higher-gluten wheat that the article describes. Really, i need more data.