They do (of sorts), see: http://successfulsoftware.net/2009/07/07/a-test-of-cost-per-action-cpa-vs-cost-per-click-cpc-in-google-adwords/ http://successfulsoftw

They do (of sorts), see: http://successfulsoftware.net/2009/07/07/a-test-of-cost-per-action-cpa-vs-cost-per-click-cpc-in-google-adwords/ http://successfulsoftware.net/2009/07/07/a-test-of-cost-per-...