Mine has ranged from a low of $3.37 to a high of $13.31. On most days it hangs around the $7.00-8.00 range.
The "wisdom" around HubPages seems to be that we should write in "competitive" titles and subjects, but I am not so sure. When I publish a hub on a "popular" subject (like "writing"), my CPM immediately takes a dive, until the initial traffic boost settles down. If I write a highly specialized hub, my CPM typically rises, even during the initial increase in traffic. I think specialization and focus is the key, e.g. don't write about "smartphones" write about "pink Nokia smartphones between $150 and $200."
I am looking to branch out my topics (currently very narrow) in coming months, so it will be interesting to see how that affects CPM.