rgrenaderphoto Loc: Hollywood, CA

Apparently, this is why I spent $350 for the OEM grip:

https://nikonrumors.com/2018/02/12/update-you-cannot-get-9-fps-with-the-new-vello-bg-n19-battery-grip-for-nikon-d850.aspx/

Oh, at Samys Cameras in Los Angeles, the D850 grip was in stock.

mas24 Loc: Southern CA

Late last year, it was said on this forum, that the entire battery grip kit for the D850 would cost over $900. The D5 battery and charger were also required. If the Vello grip does not give you those extra 2fps, why buy it except for showing it off.

MT Shooter Loc: Montana

As per Nikons own specs, the new EN-EL 18B battery is needed, the EN-EL 18 & EN-EL 18A will not provide the extra speed. Also, the operator MUST select the grip battery as the primary battery or the camera defaults to the EN-EL 15A battery in the body as the primary. I have already had a few customers who made that mistake.
Also, I get 9fps using the EM-EL18B battery in a Traymor grip I bought on Ebay to compare performance with the Nikon grip. It surprised me, but its definitely knock off quality when it comes to build.
Another battery I tried was the DSTE brand because it comes with the battery adapter and its own charger for a total of $39.95. Works good but only 7fps in either grip. The battery is the key.

rgrenaderphoto Loc: Hollywood, CA

I use it for loooooooooooong timelapses and video.

mas24 Loc: Southern CA

OK.

Robert Bailey Loc: Canada

The difference between 7 fps and 9 fps wouldn't matter to most photographers.
I presume that the 3rd party battery grip is hundreds of dollars cheaper.

rgrenaderphoto Loc: Hollywood, CA

The design intent of the D850 was as a Professional tool. Sports and action Pros need that 9 fps.