Your local health food store sells millet flour for $8/lb and brown rice flour for $4/lb. Sorghum flour can run you $7/lb, too. What's the frugal celiac to do?
Shop in ethnic stores! Indian (like, relating to India, not Native American,) grocery stores in particular have a wide variety of gluten-free flours, including types that your local health food store will never carry, and their prices are great.
(Caveat: I live just north of New York City, and prices up here are higher than in many parts of the country. A gallon of milk, right now, runs $3.30-$4.80, depending on where you shop. Therefore, please don't say, "Oh, millet flour at my health food store is only $6/lb," because your Indian grocery store prices should be correspondingly lower, too.)
The problem with Indian grocery stores is that many of the GF flours are labeled with Indian names. These are generally labeled in the English alphabet, so figuring out which ones are our funny flours is a matter of learning a few new words.
Brush Up on Your Hindi
Garbanzo bean flour is called BESAN. A superfine grind is best. Maya, from Maya Overseas Foods, makes a nice product. A 2 kilogram bag (= 4.4 lbs.) was $5 in my local Indian store, which works out to $1.14/lb. I substitute besan for garfava flour because I think the flavor is milder and it works as well or better.
To contrast, Authentic Foods Garbanzo bean flour from the Gluten-Free Mall is $6.62 for a 1.25 lb bag, or $5.30/lb, plus shipping and handling.
Sorghum flour is called JOWER flour. Kanaiya brand is a a soft, well-ground, light beige flour. Avoid brands were the flour looks lavender. A 2 lb. bag from my local Indian store was $4, or $2/lb.
To contrast, Authentic Foods sorghum flour from the Gluten-Free Mall is $6.38 for a 1.25 lb bag, or $5.10/lb, plus shipping and handling.
Millet Flour is called BAJRI flour, and Jalpur brand makes a good grind. A 1 kilogram bag, (2.2 lbs.) from my local Indian store was $5, or $2.27/lb.
The Gluten-Free Mall doesn't list millet flour, but my local health food store charges $6.50 for a 2 lb bag, which works out to $3.25/lb.
Finding Little India in Your Neck of the Woods
Your best resource is still your local yellow pages book. If you live in a major city or a university town, you probably have an Indian grocery near you.
However, the internet has its tentacles in everything nowadays.
Online Indian Grocery Store -- Delivers to your front door
Author of CALLOUS: A Novel, a story about free will, neuroscience, fate, Schrodinger's Cat, and the End of Days.