I joined the coco coir crowd for my larger container grows.Pro Mix I still use for the delicates(erbs,flowers etc.)The prices are decent for a commodity(inexpensive)medium for production.A local hydro store sells bales(3.8cu.ft)at $18.00.I do not have any connection, but see below for some value engineering for larger growing regimens.
http://www.earthscapeusa.com/online-store-1