Amazon is ending it's 20% off deal on video game pre-orders and I can't say I'm surprised. Video game software sales are a low margin segment anyway, and discounting new games by 20% absolutely made it so Amazon was losing money on every game sold.

My suspicion is that this promotion was implemented to get more people signed up for Prime and/or to improve Amazon's share of the video game-selling industry. If you get your games from Amazon, you're more likely to also get your accessories from them, which is where the real profit margins lie.