D800/600: Why not dump buffer into the TWO cards simultaneously?

Too much technojumbo.  Here's an idea:
Why doesn't Nikon just MAKE it so it can write simultaneously in the first place.
It probably costs fifty cents to put another doo-hickey on it for the thing-a-bob.
That's should solve the problem.
And fifty cents is more than worth your time of waiting.  
Hell, even a couple bucks is worth it over time.

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Sincerely, GlobalGuyUSA