It is significantly cheaper to grind your own specialty flours but you need a grain mill to do it.  A bag of organic quinoa flour from Bob’s Red Mill is $6.19.  You can buy a pound of organic quinoa at Trader Joe’s or even Whole Foods for $1.00.  So at 25% of the cost of buying the flour you can grind your own - with the added bonus that the flour is completely and absolutely fresh.  Just about any specialty flour: amaranth, coconut, almond, barley, brown rice, black bean, corn, spelt, millet, oat,  and rye to name some can be quickly and cheaply made yourself.

A good grain mill isn’t cheap though so a purchase of this type probably makes more sense for someone who plans to use non-wheat specialty flours on an ongoing basis.

The grain mill can also be used for other things including, of course, grinding your own wheat.

Back when I ate soy - I ground up soy beans and made my own homemade tofu using the recipe from The Farm cookbook.  The mill easily handled the soy and worked perfectly for tofu making.

We bought the Jupiter Family Grain Mill 8 years ago and are very happy with it.  You get quite a bit of control over the coarseness / fineness of the flour grains and the machine is sturdy, simple to put together and take apart, and clean.  I see that some website are selling it for around $200 and that sounds about right given inflation and what we paid for ours.