They could sell a boatload simply putting it out on the PC though, especially since a direct port of the 360 version would do for most SW fans. I don't know the intracacies of Xbox 360 development but with it using DirectX I suspect the path from it to PC and vice versa isn't as onerous as development for several disparate platforms (as they have already done).
I don't really buy that the reason they didn't release it on PC was because they felt it couldn't compete with previous SW titles, my gut feeling is that the decision was driven by piracy first and foremost - whilst I know 360s can be chipped I would think that with Xbox Live being a factor in this equation that they would be a relative minority. There's no piracy at all on the PS3 and from what I can gather Wii and DS piracy involves jumping through hoops.
Or it could be that the control mechanism, targeting system and QTEs wouldn't translate very well to mouse & keyboard?...