I don't have a lot of experience with freelance sites (I watched the small business I work for use 99designs for something) but just something I thought of to try to solve the problem of unrealistic underfunded projects, not sure if anyone does this:

Have a little up/down box by each project where browsing freelancers can rate if they think it's a good price or way too much for what they're asking. If an unknowledgeable project submitter gets a 10/10 or so feedback ratio they could feel pretty good about their submission, but if they get 0/30 they might realize they need to raise their price a bit.