I've used freelancer for hire sites to get specialized work done, and they're not horrible from the hiring end.
Here's what I would do to fix things on the freelancer side - establish a minimum price per hour/price per project. Think about "The Ladders" - a job site that established itself as only for job seekers for $100,000+ jobs.
What if the market was only $75/hour and up? And both developers and clients had to be invited?