The answer you are looking for is: parking revenue only really applies to domains with type-in traffic. Type-in means, direct visits to your site through the browser. Parked pages, for the most part, do not rank in Google, or at least won't do forever and so require a user to visit via type-in. For type-in visits you need a strong domain with a common ext, preferably .com. If you are looking to make revenue from keyword domains that are not .com or popular geo extensions then you need to develop them and get them ranked in Google.