I ended up buying an Xit grip for my D800 and it came with two batteries, all for about 60 dollars via ebay.
How could I possibly go wrong with that deal?
Well, actually you might be surprised at the quality of it. I have been pleasantly surprised. Fit and finish are excellent. It works properly, no issues of any kind so far.
It's hard to justify the 616 dollar cost of the genuine Nikon product when I can get a perfectly good equivalent product that works fine for 10 percent of that.
I'm all for buying the real deal, but when you pay 10X as much to get the Nikon name, you have to at least give the cheaper one a TRY first. I'd have to bust up TEN of these suckers to spend as much as I would to get the Nikon grip, and my suspicion is that I'll never bust 10 of them.