Well, the idea was that Force Powers from a different alignment would cost more, but that good idea was watered down in delivery, like every other one.
For a start, the difference was about twenty percent (four points out of twenty), and secondly it could be counteracted by good Charisma. Thirdly, there were no maxima to the bonuses added to attributes (like in NwN, for example, where no more than twelve can be added to a single attribute), so the entire system was skewed into infantile difficulty modes of gameplay.