There are a bunch of articles on pricing leaf cleanups on my blog here
Check them out, I am sure they will help.
Keep in mind your expenses will differ from others. The lower you can keep your overhead costs, the lower you can get away with charging and still make a profit.
Also, play around with the lawn care business estimation calculators here http://lawnchat.com/?page_id=341
They should give you more insight.
Keep us posted on how all the marketing goes. I want to hear more updates