Thats a very subjective question you're asking. there no such thing as a cutoff for 'good' traffic. For example you can buy 1000's of poor quality hits, very cheap, that won't convert... or you can try and rank organically for buying keywords.
Just to give you an idea, I'm a member of a few CPA networks and most my sites generate between 70 - 150 unique hits per day by being ranked organically.
Like the guys above said, its the conversions that matter.