On some ads it says $0.20 Cost or max bid but when its clicked I only get $0.04. Whys that? Also with Interstitial and CPM Banners. Do I get money per impression or do I have to show that advertisement 1000 times before I earn anything?
Earnings depend on the quality of the traffic - like where it comes from. Traffic from Outer Mongolia pays less per click than US traffic. You get CPM earnings as and when the impressions occur - for example, if you only display 500 interstitials at a CPM of $2, you'll get your $1.
Also you get only percents of the bid. AdBrite keeps commison for itself and you don't have control over it.