I heard they pay a certain amount of $ per 1k impression, like $3-$5 is that true? I thought they were a CPM..
That is CPM. CPM pays on a basis of 1000 impressions. So if they run $1 CPM, that means that they will pay you $1 for 1000 impressions.
$3-$5? You wish! LOL. It's more like .50 cents CPM across the board, and I've been with them forever. The best thing about Fastclick? You could put their banners just about anywhere and they don't really care. Or at least they haven't cared for the last 4 years I was with them.