KH3 doesn't look like the most expensive game ever, and it's clear that games like FFXV and FFVIIR have a much bigger budget. It wouldn't surprise me if 3 million copies overall would be all they need to sell for the game to be considered a success, it'll sell more than that, I predict around 5 million if they play their cards right, but I really doubt that it's going to surpass KH1 in terms of sales.
I'm now filled with determination.