I know that a friend of mine gets a lot from the Dollar Tree and Big Lots. And if you live near a good factory store, like Mattel or Malden Mills you can get great deals.

I go to second hand stores here in Sacramento where I find Hanna and American Girl etc for $1.00 -- but you never know, it's hit and miss.
You just have to sort of know what to look for. I'm a hit and miss kind myself. Things I think will never sell go high and 'sure fire' hits are duds. I dunno!