Canon has, indeed, gone crazy with the pricing for the Battery Grips. If they actually came with the respective batteries, it would be an easier pill to swallow, but they don't.
Has anyone had any success with any off-brand batteries yet? I've seen several reports of camera/battery communication issues. I usually buy an extra OEM battery so I have 2 for a grip, and an off-brand backup set. But it looks like I may be waiting a while on the 6D...