Doctor Venkman;142648
Yes, Sony gets money from the sales of the game, but I assure you they don't get as much from a copy of the game selling on 360 as they do from a copy of the game selling on a PS3.
They may not make as much money if the game is on other consoles, but they do lose a good revenue from it which they could have made from those other sales.
If I was a business owner, I would open my revenue up as much as possible because even the small amount is better than none at all.