Adderall isn't like pot, where prices seem to remain consistent throughout the world. Some schools have many kids with ADD who are willing to sell.. and others have virtually none.

Ask around if other kids have it, and if not, then 50 dollars for 10 pills might not be a bad deal. But, maybe the quiet kid in English class will sell you 10 pills for 30. You just never know.

Edit: Personally, I can get them for about 2 or 3 dollars each, without options to buy in bulk. But I go to a school of 2,000 and it seems like 1/3 of the entire school population seems to have some sort of attention defecit disorder.