See the blog I wrote on how to price a foreclosure cleanout/trashout service: http://www.trulia.com/blog/don_tepper/2010/06/foreclosure_trashout_cleanout_bidding_6_steps_to_a_profitable_business
The concept is the same. You determine what your time is worth per hour. You determine the number of hours it'll take. You add in supplies. You add in expenses of any other labor you have. And you add in a percentage for your overhead and for profit.
The only "tricky" part is estimating the number of hours it'll take. Other than that, you'll already have all the information you need.