Having successfully procured contracts for proposal writing through Elance, Freelancer, and oDesk, I agree with Craig that defining your targeted customer is extremely important and even more so now that competition is global and platforms such as Elance enable instant connections between clients and contractors. Many potential clients on platforms such as Elance, Freelancer, oDesk, etc. are purely looking for low-cost contractors. As your business doesn't sound like one that is willing to compete on price, then you need to pursue potential customers that are willing to pay a premium for your services.

In my experience on these platforms, you can generally tell the willingness of a potential client to pay a premium by the effort they put into the job description. A simple one sentence request for proposals is probably coming from a potential client that is looking for the cheapest contractor. On Elance you can also pay for a premium membership allowing you to see what budgets other freelancers are submitting. This will enable you to see if you can be price-competitive. Finally, I have also had clients come back after working with a low-cost contractor whose quality of work wasn't satisfactory. Some potential clients may realize that they get what they pay for. So, it doesn't hurt to submit some proposals in which you may be at the high end of cost - it's a good way to get your name out. The client may come back to you.

Good luck with your efforts. Please get in touch with me if you want more details on how I approach platforms such as Elance for my business.
-Gareth.