The Bottom Line and How We Figure It
Here's the basic deal: We don't bill you as if we developed your site from scratch. What we do instead is present you with an advance quote based on our assumption of how many hours a job will take to complete. If it takes longer than we expected, thats not your problem: we'll stick to the original quote.
It doesn't matter what anyone tells you. With a few notable exceptions if you design something once you can dress it up a little and plug it in again elsewhere. If you are experienced in actual systems programming, and have moved from that to web design (like we did), writing code that facilitates this is second-nature.
Monthly Maintenance Fees
We get pretty burned up over this whole concept. We don't charge regular maintenance fees. If you need work done, we'll give you an advance price quote for the work and, if you agree the price is fair, we'll get to work.
Otherwise we keep our mitts off of your checkbook. The reality is that, for the designer, this is an excellent cash cow that involves little effort on their part, other than that needed to endorse your monthly check.