I saw this pin that said if you cut the cover off an Energizer A23 battery there are 8 watch/calculator batteries inside. I haven't tried this out, but I wanted to share it. If this is true, it can save you a lot of money in the long run.
A battery doesn't cost much. $5 for a pack of two, right? A watch battery is about $5 on its own. $5 worth of A23 batteries will give you 16 watch batteries (worth $80). That saves you $75.