SEOMoz stated they charged $1000 / hour, but they have now changed their business model and focus exclusively on software vs. services. They sold their service side of the business to distilled. Here is a good video post (2010) from distilled on how to choose a SEO Consultant.
I know a star who did SEO/SEM for an agency back east and then worked at a consumer site with over 10 million visits / month doing all their SEO and SEM. I use him for SEO/SEM consulting for my company. He is really focused on what you need, not doing a lot of B.S. And he's well rounded so he's got excellent perspective on things related to marketing and sites.
In terms of rates, I would guesstimate the range is from around $75/hour to $100ish or so. But certainly I'm sure you'll find folks less expensive than that. Others will jump into the thread with more info on that.
Let me know if you think you'd want to contact him.