I don't know if it's so much affluence as what the manager percieves is the ethnic base. For instance, our Walmart has a fairly large Mexican foods department (and Kroger, on the other hand, has virtually none).
For flours, check out Wisenberger Mills,
Weisenberger Mill They're right here in Midway, as it turns out. But you can mail order.
Like everyone else, they've had to raise their prices. But they're still affordible. 25 pounds of bread flour are something like 15 bucks. On another list somebody was complaining that he couldn't afford to bake, not when bread flour was more than a buck a pound. So I reckon Wisenberger still has the best prices.
Not only that, but all their wheat is purchased from Kentucky growers!
Until the big gas price run-up I would just drive out there (only about 45 miles, for me). It's a fun place---a water-driven mill on the banks of the S. Elkhorn. In fact, my next back-page column in Kentucky Gardener will feature them.