My organisation is hoping to run a hackathon event in a few months time. We're a public organisation and we have lots of data and ideas how this might run but we need someone to direct and basically run the event. How much do people usually charge for this - the estimates we've had seem rather expensive!
One resource I have sent many people to (and they always find value in it) is Socrata's* "hackathon in a box" guide: http://hackathon-in-a-box.org/guide/
The Open Knowledge Foundation also has a guide which I have not read as closely at http://blog.okfn.org/2012/10/26/hackathons-the-how-to-guide/.
And finally, please at least skim ChallengePost's blog post titled "Hackathons ≠ developer exploitation. A what-not-to-do guide for good hackathon organizers."
*Full disclosure: the company I co-own is a partner of Socrata and they have sponsored hackathons we have helped organize.
The School of Data has an active community of volunteers that you can engage for either free or very reasonable pricing I presume. Their website has great material (open to use and distribute) made as starter kits that can get you folks up and running as well.