The Rise and Fall of Spyro

What happened to Spyro games for Playstation between October 2007 and January 2008? The resale prices for every PS1 Spyro game increased by at least 100% during this time. At first I thought it was Christmas, but Christmas 2006 (the far left side of each chart) shows almost no price change at all from December 2006 to January 2007. So it isn't just a seasonal increase in demand for Spyro games. Spyro Enternal Night was released in October 2007. Is that the sole reason for a price spike of more than 200% in some cases? If you have any other ideas for what caused this huge price increase last year let us know by leaving a comment.