I'm a freelance front-end dev in Australia. I currently get paid $420 a day. I have no idea how much the recruitment agency who placed me are skimming off the top.
I can't shake the feeling that my rate is at the low end, but because of the secrecy between other devs and the recruiters I have nothing to gauge myself against.
Am I being shafted?
That said, intuitively I feel that is insanely low. If you are framing yourself as a consultant who can solve quantifiable business problems using frontend development, then ~$400 per day is absurd. I would say increase regardless of your living costs. Asssuming 30 weeks of utilization, you're working for $60,000 per year. If you're doing remote freelance work then you can target US companies and literally quadruple this.
I live in NY and I charge between $1000 and $2000 per day for information security services that normally take 2 - 4 weeks per engagement. Mind you - information security is a specialization that is not as quantifiable as developing a website for business purposes, so in theory you should be able to achieve higher rates than that (Brennan Dunn, as an example, charges $20,000 per week as of 2014, and he does a mixture of web development and copywriting).
If you follow 'patio11's advice you can certainly increase this. The beautiful thing about being a consultant is that you can choose to work remotely, which means you can anchor your cost to the living costs of your client's location. I'd be charging the same if I lived in Kansas.
Increase your rates, and if necessary rebrand/reframe your value proposition. Also - get rid of the recruitment agency. Agencies can be good, but you need transparency regarding your rate and how much they are taking for placing you. You should also try to develop a strong personal network for referrals.
You will know when you're successful because you start saying no to potential clients as much or more than you say yes.