"CheapBatteries" can be good as well as other sources. The most reliable way I've found is to visit a variety of good merchants whenever you want them. Chances are someone will have them slightly cheaper than others.
It is frustrating because Energizer has a near-monopoly on Lith AA's which leaves us with few alternatives. It's very different with 123's where there are many options including splitting 223's.
Near monopoly???? As far as I know, it is a total monopoly, brightnorm. Cheapest retail store is Walmart (that I know of). Best deal if bought in a minimum of 48 is cheapbatteries.com.