It depends on what your portfolio looks like, honestly. If you've got a bang-up portfolio, by all means do the $150-$200/hour people are recommending.
If your portfolio needs a little more polish, charge lower to get the experience.
When I started freelancing, I would purposefully undercharge and over-deliver, and let the client know that.
If you need to turn work down while you wait for those kinds of higher-paying gigs to come along, you can always sharpen and hone your skills by creating ecommerce templates for theme stores, and make money off of those sales.
It may not be the _most_ profitable, but it will keep you in practice in-between clients. The most important thing is that you remain prolific in your work and create a large body of content.
Not for them, but for your own skill set.