Dislike is exactly what downvoting was intended for. You're free to use it for whatever reason you want. You should have known this already, the verbiage regarding flagging when one tries to flag is simple enough that one can understand that much. You SHOULD flag because you don't agree with how much something is making(reward) after all, much less because you disagree with them, heck, the only argument that exists here is that people are free to upvote as they please, but they shouldn't downvote as they please, because "rewards" or whatever.