I'm looking for some input an various powders and trying a happy medium between cost and volume.
What's your application? Power Pistol might be THE best powder if you want to shoot 115gr bullets at 50 yards for accuracy, but I'd never recommend it for a plinking load, defense load, or 9mm minor action pistol load.
Is this basic target shooting? If it is not, let us know a more specific application. Everything else in this post assumes basic target shooting at short to moderate ranges -- out to 25 yards.
First, you should be looking at Alliant, Accurate, Ramshot, Hodgdon, and Winchester. In terms of history, load data, and price, these are your best options for manufacturers. If you buy in 8lb bottles, you can get Alliant around $16/pound before shipping and hazmat, Winchester at $19/pound, and the ones in between priced in between.
Second, the faster the burn rate (generally speaking -- this will not be true with every bullet in every caliber) the less powder it takes to reach a given velocity, which means lower powder cost per cartridge. So while Power Pistol and AA7 and Silhouette may be outstanding powders for certain applications, they're not going to be the cheapest.
You can and should make your own cost charts per Wobbly's suggestion.
If you are looking to shoot 124gr bullets at less than 1100 feet/sec, powders like Bullseye, AA2, HP-38/Win231 will be where you want to be. Sport Pistol is a newer, cleaner powder getting a lot of good chatter, IS in a good burn rate range (similar to HP38), and I wouldn't hesitate to buy it if I saw it, and it's Alliant, so inexpensive if bought in bulk.
You'd be best off picking one of those powders, sucking it up, and buying 16 lbs right off the bat to defray the hazmat and shipping fees. Buying a pound or two at a time locally costs WAY too much over time.
I'd stay away from Titegroup. It's filthy except at max or +P loads.