So today I was trying to do a wit and the LHBS I use was out of rice hulls. Anyway my gf has a horse and says they have huge bails of rice hulls there.. so we went and 6cuft of rice hulls was $10. I took as much as I could conceive needing in the near term and she took the rest to the horse.
I'm made a tea of "brewing" rice hulls and the ones from the feed store just to be sure they haven't been treated differently and really can't tell the difference.
So unless someone comes up with a good reason not to use it, seems like a way to get a crap load of rice hulls cheap.