There are big price differences even on the oem models.

I know some of them are junk and will explode in my face, but come on! $90 for the battery?

The electronics retailers must be making a killing off of these.

http://www.google.com/products?q=cga-du21+panasonic+battery&btnG=Search+Products&show=dd

I think it’s a big scam, like printer cartridges! They know that once you own the camera, you have no choice but to buy their batteries, so they can just screw you on the price.