These are my trusted sites.
http://hispasolutions.com/index.php?route=common/home
http://gamebuyers.ru/index.php?route=common/home
BF3 RU--- 12.99€
BF3 EU --- 13.99€
Premium----35.00€
BF3+Premium Edition(Game +Premium+DLC)---------45.99€
This is really cheap I always buy my keys there.