Amazon.com has a nice subscribe and save deal going on for the 8 Pack of Rayovac AL9V-8 UltraPRO
Alkaline 9V Batteries for $9.96 shipped. That translates to $1.25 for each 9V battery- a very good price for a name brand alkaline. I was looking at eBay and found 12 packs for $10, but it turned out that they were 9V Carbon Zinc
batteries which have much shorter shelf life than typical Alkaline. The cheapest 12 pack alkaline 9V I could find on eBay was about $18 for some unknown brand. So I think it's a no-brainer in this case to go with Amazon and a brand like Rayovac. You get much faster shipping as well so you don't have to wait 2 weeks for your batteries to arrive from China.