I don't list prices on my website because as others have stated, it can scare away potential clients as well as make other decorators/designers try to undercut. One of the first questions I'm asked when they do contact me by phone and/or email IS price however. (sigh!...sad but true).
I'd really like to have other pricing options besides hourly, which is what I currently do, but found that if I only charged a percentage, I made little to no money for all the hours I'd put in on a project. Most of my projects to date have been redesign with a few new things added. Also, in our area (upper Midwest) people are just more familiar paying hourly rates as opposed to a rather "uncertain" percentage idea. They wonder "based on what, how much does that ordinarily come to?" and other questions such as these.
I arrived at my hourly rate by more or less comparing my work to other service-oriented businesses in our area. That way it looks comparable to what customers are used to paying hourly, even though my services are entirely different than say boat repair, auto mechanic, house painter, etc.
So far, I've been pretty happy with the results of this decision...and so have my customers

After five years as a decorator (Sheffield grad) I've sorta been able to assess a prospective project and give at least a ball park figure on what it might cost. From there, and the client's "proposed" budget, we usually come to some agreement for the project. My ultimate goal is make my customers happy and of course to end up with a profit for me
Connie Nikiforoff Designs