This game is slowly getting to be hard to find (at least a new copy at a reasonable price). The new copies at Amazon are starting to sell at crazy prices through the third party merchants. Walmart has them now for pretty cheap 21.96.
http://www.walmart.com/ip/Professor-Layton-and-the-Diabolical-Box-DS-Nintendo-DS-Dsi/11989512
http://www.walmart.com/ip/Professor-Layton-and-the-Diabolical-Box-DS-Nintendo-DS-Dsi/11989512