Not only is Halo 4 an incredible game, there are rewards for playing it too. Microsoft has announced that Xbox Live Reward members who reach certain amounts of playtime on Halo 4 will get Microsoft points. That's right, just for playing you get free money. If you aren't a member, sign up here.
In addition, you also get refunds for MSP spent on Halo 4 content. Spend 1500 MSP and get 100 back. 3000 nets you 200, and spending 3000 plus playing 35+ hours will get you a cool 800 MSP.
So get out there and make yourself some digital dough.