So you've researched all of the highest paying AdSense keywords, built your sites, and you're waiting for the cash to come rolling in.  Here's a clue -- you're going to be waiting for a LONG time for that cash...

The problem is that EVERYONE is doing exactly what you're doing - targeting the highest paying keywords.  Forget about the highest paying words and focus on the lower tiers - the competition is lower and the number of searches is much higher down there...