Pricing metrics used for application development

I'm rather new to application development and primarily work as a Systems Engineer. I have been using REBOL for about 2 years now and luv it. Now I'm ready for another step. I want to start making some $$$ for my efforts. Can anyone provide some form of pricing metrics that they use to determine how much value to place on development of applications. The more detail the better. Weblinks would be very useful as well. Thanks in Advance. Paul Tretter