From several months before Pokémon Diamond and Pearl launched Pokémon fever began hitting the United States. The chart below, from Used Video Game Pricing, shows that while prices for used video games in general dipped more and more from February, all used Pokémon games saw an increase in average price due to the demand for these games.
Some Pokémon in D/P can only be obtained by transferring them from Pokémon Ruby, Sapphire, FireRed, LeafGreen, and Emerald. This is likely a huge contributor to the increase in used Pokémon game sales. Maybe other people simply wanted to try out the older games before the new DS games were to come out. Do you think there are any other reasons?
