I have ZERO interest in grip.
My 2cents; If I can afford mrk III, I would buy legit grip + battery. Why take that risk on Chinese grip???
You spend $3499 for a camera, $60 for an extra battery, but won't pay $90 for a case to hold the two batteries in, but you would rather spend $350 to be able to do the same thing. SMH. If you want to spend the $350 on case to "hold" your batteries, then so be it, just know that it probably costs Canon about $30-$50 to make it, and if you don't have an interest in a grip, don't worry about the cost, it'll still be there when you decide to buy one.
My 3 cents
P.S. take no offense, just offering satire