It depends on who does the redesign, how complex it is, and who implements the skin. Check out
www.templatemonster.com for designs that good and reasonably priced. Then, once you find a skin, you can just ask for a quote in the forums and someone will give you a price, then go from there. I usually plan on 10 hours or so to implment a skin, of course, it always varies depending on the complexity and depth of the changes.
Hope this helps!
--Kurt