I don't think it's impossible for them to profit with less than 4 million sold and keep this game exclusive. To sum up my thoughts with another Neogaf post:
The amount of revenue they get differs from publisher to publisher. Square Enix does not have to pay royalties to the studio developing the game because it's being made internally. That's one advantage of that. These guys have been in business for decades now and have solid distribution network set up in most countries. Yes, they need to pay the platform holder some royalties and other costs, but even after that they will get more than $40 per game. Also, at least 30% or more copies will be sold in Japan where the game would cost (after converting) $80-$90, so that would be profitable for them. Final Fantasy XIII, for example, was almost $89. It's a complex thing, really.
Either way, this opens the way up for Versus XIII to remain what it was always meant to be and we get Agni's Philosophy as FFXV and a Durango / PS4 multiplat.
