I get most of my regular "supplies" at wall-mart. Their in-house pharm brand is TopCare, and they sell generic talc, corn starch, lotion, etc for half of what the J&J goes for, and I can't really notice any difference.
I also swung by the dollar tree recently to grab a can of Angel of Mine air freshener, someone here said it had the perfect diaper smell. When initially sprayed it's a little off, but given just a little time to dissipate and the room smells great! I also picked up some talc, it was a buck for a 14oz bottle, which is about 1/2 the capacity of the big topcare/J&J bottles. iirc wal-mart gets about $2 for them, so the price is about the same.
But as for this "liquid baby powder"... what is it? is it like a fast-evaporating spray or lotion that leaves behind a powdery residue? Or is it more like a regular lotion, or oil?