The 5200+ cost more because it's an old and outdated chip. Newegg tries to clear their inventory/stock of old products that way, while still trying to make a profit.
Besides, the one I showed is the Athlon II X2. And it's faster than the Athlon X2 5200+.
Yep, completely new architecture. The 5200+ is 65nm, while the 240 is 45nm. Basically, the 240 will run rings around the 5200+, but it is cheaper to produce as the smaller die size allows them to end up with more chips per disk of silicon.