I used to think this when I first started using RentACoder. Then I thought sod this, and started giving quotes at my full-whack rate, and you know what? It worked, and it's continuing to work :)
One bit of advice I'd like to add: don't be put off if the price listed for a project is a bit below (or even way) below what you'd like to charge; I find a simple email with questions, a rough timeline and then basic explanation of why your quote costs so much (you need to work for a while at a good rate) works well. Good luck!