This means that the attacker has to regenerate those 300 billion billion possible results to get your salted passwords. And if you use unique salts for each user, that means 300 billion billion per user account!!
If the attacker knows the salt and the seasoning process then a weak initial password is still a weak initial password md5($salt.'password'); is no harder to brute force than md5('password'); & it won't take 300 billion billion anythings to crack