The only real place within Manhattan I found was Kinokuniya, but they're stupid prices. If its at all possible to get a subway over to Flushing (Queens), there's a place called "Anime Castle" which was awesome. I ended up spending quite a bit there, and whilst it's a bit out of the way, the Chinatown district of Queens >>> Chinatown in Manhattan. If I remember correctly, it's something like a 30-45min subway ride each way, so it might be possible. Within the island of Manhattan though? Yah, expect to pay silly prices. As in, you might be better off ordering online (unless it's actually impossible to find online) kinda prices.