For some of us in cities with little competition, I would kill for 5cpm. To get lower than that I usually have to add a "positioning" flight which usually has awful cpm value. For example, on the farecompare/flyertalk page, I have no current fares from my home city under 6cpm. Even those are only a short list of Asia/Austrailia long hauls, everything else is 8cpm or higher.