As a (very) small-time publisher, but with a fairly reasonable sample over the years, CPM ads pay about 1/5th what CPC ads do. I think that shows how much "brand awareness" versus "I'm trying to make a sale" advertising is worth.

Edit: CPM pays 1/3rd the rate, but CPC ads make up 90% of revenue, which makes sense if they generally pay more. I run a rather diverse set of sites, but I stay away from tech.