Well the other thing to consider is these ports have a very low development cost. They're just reusing the same exact assets on similar class hardware, it's not like they have to build these games from the ground up.
Even assuming lets say 2 million total sales for a game like Rebirth on Steam/PC + Switch 2 combined (XBox also?), 2 million at an average profit of say $25/copy for Square-Enix is an extra $50 million in revenue for a low cost port. That can be a huge chunk of the development budget of the game, assuming say like a high budget price like $120 million for FF7 Rebirth (PS5 version), an extra $50 mill added to the pile can swing the game from being unprofitable to having made a profit or barely profitable to at least a half decent margin.
Because you have basically very little dev cost on ports to new platforms it means extra sales go quite far in adding to your net profit for a game.
It can also pay for a lot of the dev cost of FF7 Remake Part III.
