Every gamer knows that Halo 3 was released for Xbox 360 on September 25 because it was almost a holiday in the gaming community. It sold 3.3 million copies in the September alone. A large number of these millions of buyers decided to prepare themselves for Halo 3's release by playing the original again. Prices for the original Halo went up almost 30% in September, going from $7.15 in August to $9.14 in September.
Plenty of gamers must have gone nostalgic after playing Halo 3 too, because the prices just kept on increasing in October. Going up another 10% during October to almost $10. But just as quickly as the price went up, gamers appetite for the original faded and the price dropped back down in November.
Moral of the story: If you going to relive your old gaming memories, buy it before everyone else does. You'll save a few bucks.
Video game price data provided by VideoGamePriceCharts.com