I just checked out my local pool store and they can get sodium hypochlorite 12% in both 5 gallon and 15 gallon containers. The larger size comes in a returnable Carboy and costs $47. A small diameter spigot is free or you can buy a larger heavy duty 2" one for $25.
It seems like a reasonable deal so I'm wondering if anyone had any experience with this. I called the chemical company that actually supplies the stuff and they say it comes in 3 times a week from the factory about an hour north of where I live so it should be quite fresh. They promised to send over a chart showing how fast the stuff loses potency but I haven't gotten it yet.
It seems like an interesting option. If nothing else it saves a lot of trash in the form of gallon containers.