CSS Ninjas provide a service for converting designs into XHTML/CSS. Their site features a nice cost estimate tool that allows prospective clients to see how much it will cost by specifying the number of pages that need to be converted. A slider allows you to estimate the cost of 1 to 20 pages. Clicking the "proceed to checkout" link opens the request for quote, and you can enter a number above 20 if required.

1. The cost estimate slider.
2. Moving the slider right.
3. Viewing the request for quote and modifying the estimator form manually.