So who charges the least in royalties? MS? Sony or Nintendo? Or Apple when they release their console ? (lol).
People should also consider "money hatting" or some sort of favoritism companies get. Splinter Cell Conviction, even as a timed exclusive, must pay a bit less royalties towards MS or get some sort of free promotions. I believe MS paid Namco quite a bit to put Tales of Vesperia exclusive for several years for the 360, and so on.
It's just that simple.