I think there should be bigger rewards the higher killstreak you're on, normally you'd get 325K/650K each kill.
But my suggestion is, If you're between 10-19 killstreak, you should get +25-50K more, until you hit 20-29 killstreak than add an additional +25-50K, so the higher killstreak you get on, you get a tad bigger reward for the kills.
Could also be done with the wildy points, so instead of 300 at 10-19 killstreak, you'd get like +10-25 each 10 kills you go up?
Only thing going up with killstreak, is the reward for killing the guy who's on it, which doesn't really benefit the guy who has the killstreak.
